Search2024 Vol. 31, No. 5
Display Method:
2024, vol. 31, no. 5, pp.
826-832.
https://doi.org/10.1007/s12613-024-2870-3
Abstract:
Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process, high mechanical and electrical comprehensive performances, and low cost; thus, they are widely used in high-speed rail contact wires, electronic component connectors, and other devices. Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys. Taking the typical solid solution-strengthened alloy Cu–4Zn–1Sn as the research object, we proposed using the element In to replace Zn and Sn to achieve low alloying in this work. Two new alloys, Cu–1.5Zn–1Sn–0.4In and Cu–1.5Zn–0.9Sn–0.6In, were designed and prepared. The total weight percentage content of alloying elements decreased by 43% and 41%, respectively, while the product of ultimate tensile strength (UTS) and electrical conductivity (EC) of the annealed state increased by 14% and 15%. After cold rolling with a 90% reduction, the UTS of the two new alloys reached 576 and 627 MPa, respectively, the EC was 44.9%IACS and 42.0%IACS, and the product of UTS and EC (UTS × EC) was 97% and 99% higher than that of the annealed state alloy. The dislocations proliferated greatly in cold-rolled alloys, and the strengthening effects of dislocations reached 332 and 356 MPa, respectively, which is the main reason for the considerable improvement in mechanical properties.
Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process, high mechanical and electrical comprehensive performances, and low cost; thus, they are widely used in high-speed rail contact wires, electronic component connectors, and other devices. Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys. Taking the typical solid solution-strengthened alloy Cu–4Zn–1Sn as the research object, we proposed using the element In to replace Zn and Sn to achieve low alloying in this work. Two new alloys, Cu–1.5Zn–1Sn–0.4In and Cu–1.5Zn–0.9Sn–0.6In, were designed and prepared. The total weight percentage content of alloying elements decreased by 43% and 41%, respectively, while the product of ultimate tensile strength (UTS) and electrical conductivity (EC) of the annealed state increased by 14% and 15%. After cold rolling with a 90% reduction, the UTS of the two new alloys reached 576 and 627 MPa, respectively, the EC was 44.9%IACS and 42.0%IACS, and the product of UTS and EC (UTS × EC) was 97% and 99% higher than that of the annealed state alloy. The dislocations proliferated greatly in cold-rolled alloys, and the strengthening effects of dislocations reached 332 and 356 MPa, respectively, which is the main reason for the considerable improvement in mechanical properties.
2024, vol. 31, no. 5, pp.
833-841.
https://doi.org/10.1007/s12613-023-2805-4
Abstract:
Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels. In this work, the austenite dynamic recrystallization (DRX) behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines. The single-pass hot deformation results reveal that the prior austenite grain sizes (PAGSs) for samples with different deformation reductions decrease initially with an increase in deformation temperature. However, once the deformation temperature is beyond a certain threshold, the PAGSs start to increase. It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature, respectively. Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX. In the case of complete DRX, PAGS is predominantly determined by the deformation temperature of the final pass. It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.
Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels. In this work, the austenite dynamic recrystallization (DRX) behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines. The single-pass hot deformation results reveal that the prior austenite grain sizes (PAGSs) for samples with different deformation reductions decrease initially with an increase in deformation temperature. However, once the deformation temperature is beyond a certain threshold, the PAGSs start to increase. It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature, respectively. Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX. In the case of complete DRX, PAGS is predominantly determined by the deformation temperature of the final pass. It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.
2024, vol. 31, no. 5, pp.
842-854.
https://doi.org/10.1007/s12613-024-2846-3
Abstract:
Magnesium and magnesium alloy foils have great potential for application in battery anodes, electromagnetic shielding, optics and acoustics, and biology because of their excellent specific damping, internal dissipation coefficients, magnetic and electrical conductivities, as well as high theoretical specific capacity. However, magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure. Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks. Numerous methods have been applied to prepare magnesium alloy foils. They include warm rolling, cold rolling, accumulative roll bonding, electric plastic rolling, and on-line heating rolling. Defects of magnesium and magnesium alloy foils during preparation, such as edge cracks and breakage, are important factors for consideration. Herein, the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation, defect control, performance characterization, and application prospects. The advantages and disadvantages of different preparation methods and defect (edge cracks and breakage) mechanisms in the preparation of foils are identified.
Magnesium and magnesium alloy foils have great potential for application in battery anodes, electromagnetic shielding, optics and acoustics, and biology because of their excellent specific damping, internal dissipation coefficients, magnetic and electrical conductivities, as well as high theoretical specific capacity. However, magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure. Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks. Numerous methods have been applied to prepare magnesium alloy foils. They include warm rolling, cold rolling, accumulative roll bonding, electric plastic rolling, and on-line heating rolling. Defects of magnesium and magnesium alloy foils during preparation, such as edge cracks and breakage, are important factors for consideration. Herein, the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation, defect control, performance characterization, and application prospects. The advantages and disadvantages of different preparation methods and defect (edge cracks and breakage) mechanisms in the preparation of foils are identified.
2024, vol. 31, no. 5, pp.
855-861.
https://doi.org/10.1007/s12613-023-2808-1
Abstract:
Lithography is a pivotal micro/nanomanufacturing technique, facilitating performance enhancements in an extensive array of devices, encompassing sensors, transistors, and photovoltaic devices. The key to creating highly precise, multiscale-distributed patterned structures is the precise control of the lithography process. Herein, high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography. By optimizing these parameters, ZnO nanorod arrays with line/hole arrangements are successfully prepared. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which achieve highly efficient energy conversion in perovskite solar cells. The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.
Lithography is a pivotal micro/nanomanufacturing technique, facilitating performance enhancements in an extensive array of devices, encompassing sensors, transistors, and photovoltaic devices. The key to creating highly precise, multiscale-distributed patterned structures is the precise control of the lithography process. Herein, high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography. By optimizing these parameters, ZnO nanorod arrays with line/hole arrangements are successfully prepared. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which achieve highly efficient energy conversion in perovskite solar cells. The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.
2024, vol. 31, no. 5, pp.
862-876.
https://doi.org/10.1007/s12613-024-2832-9
Abstract:
Cemented paste backfill (CPB) is a key technology for green mining in metal mines, in which tailings thickening comprises the primary link of CPB technology. However, difficult flocculation and substandard concentrations of thickened tailings often occur. The rheological properties and concentration evolution in the thickened tailings remain unclear. Moreover, traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties. An experiment of flocculation condition optimization based on the Box–Behnken design (BBD) was performed in the study, and the two response values were investigated: concentration and the mean weighted chord length (MWCL) of flocs. Thus, optimal flocculation conditions were obtained. In addition, the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear, compression, and compression–shear coupling experimental conditions were tested and compared. The results show that the shear yield stress under compression and compression–shear coupling increases with the growth of compressive yield stress, while the shear yield stress increases slightly under shear. The order of shear yield stress from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Under compression and compression–shear coupling, the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases, while concentration increases slightly under shear. The order of concentration from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Finally, the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.
Cemented paste backfill (CPB) is a key technology for green mining in metal mines, in which tailings thickening comprises the primary link of CPB technology. However, difficult flocculation and substandard concentrations of thickened tailings often occur. The rheological properties and concentration evolution in the thickened tailings remain unclear. Moreover, traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties. An experiment of flocculation condition optimization based on the Box–Behnken design (BBD) was performed in the study, and the two response values were investigated: concentration and the mean weighted chord length (MWCL) of flocs. Thus, optimal flocculation conditions were obtained. In addition, the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear, compression, and compression–shear coupling experimental conditions were tested and compared. The results show that the shear yield stress under compression and compression–shear coupling increases with the growth of compressive yield stress, while the shear yield stress increases slightly under shear. The order of shear yield stress from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Under compression and compression–shear coupling, the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases, while concentration increases slightly under shear. The order of concentration from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Finally, the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.
2024, vol. 31, no. 5, pp.
877-886.
https://doi.org/10.1007/s12613-024-2884-x
Abstract:
Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.
Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.
2024, vol. 31, no. 5, pp.
887-898.
https://doi.org/10.1007/s12613-024-2889-5
Abstract:
Anterior cruciate ligament (ACL) injuries of the knee are one of the most common and serious athletic injuries. The widely used cortical suspension fixation buttons for ligament reconstruction are permanent implants, particularly those made from conventional steel or titanium alloys. In this study, a biodegradable Zn–0.45Mn–0.2Mg (ZMM42) alloy with the yield strength of 300.4 MPa and tensile strength of 329.8 MPa was prepared through hot extrusion. The use of zinc alloys in the preparation of cortical suspension fixation buttons was proposed for the first time. After 35 d of immersion in simulated body fluids, the ZMM42 alloy fixation buttons were degraded at a rate of 44 μm/a, and the fixation strength was retained (379.55 N) in the traction loops. Simultaneously, the ZMM42 alloy fixation buttons exhibited an increase in MC3T3-E1 cell viability and high antibacterial activity against Escherichia coli and Staphylococcus aureus. These results reveal the potential of biodegradable zinc alloys for use as ligament reconstruction materials and for developing diverse zinc alloy cortical suspension fixation devices.
Anterior cruciate ligament (ACL) injuries of the knee are one of the most common and serious athletic injuries. The widely used cortical suspension fixation buttons for ligament reconstruction are permanent implants, particularly those made from conventional steel or titanium alloys. In this study, a biodegradable Zn–0.45Mn–0.2Mg (ZMM42) alloy with the yield strength of 300.4 MPa and tensile strength of 329.8 MPa was prepared through hot extrusion. The use of zinc alloys in the preparation of cortical suspension fixation buttons was proposed for the first time. After 35 d of immersion in simulated body fluids, the ZMM42 alloy fixation buttons were degraded at a rate of 44 μm/a, and the fixation strength was retained (379.55 N) in the traction loops. Simultaneously, the ZMM42 alloy fixation buttons exhibited an increase in MC3T3-E1 cell viability and high antibacterial activity against Escherichia coli and Staphylococcus aureus. These results reveal the potential of biodegradable zinc alloys for use as ligament reconstruction materials and for developing diverse zinc alloy cortical suspension fixation devices.
2024, vol. 31, no. 5, pp.
899-906.
https://doi.org/10.1007/s12613-023-2810-7
Abstract:
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
2024, vol. 31, no. 5, pp.
907-916.
https://doi.org/10.1007/s12613-023-2794-3
Abstract:
The conversion and storage of photothermal energy using phase change materials (PCMs) represent an optimal approach for harnessing clean and sustainable solar energy. Herein, we encapsulated polyethylene glycol (PEG) in montmorillonite aerogels (3D-Mt) through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs. When used as a support matrix, 3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG. Simultaneously, 3D-Mt/PEG demonstrates outstanding shape retention, increased thermal energy storage density, and commendable thermal and chemical stability. The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating–cooling cycles. Furthermore, the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels, facilitating efficient phonon transfer. This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction. This study addresses the shortcomings of PCMs, including the issues of leakage and inadequate flame retardancy. It achieves the development and design of 3D-Mt/PEG with ultrahigh strength, superior flame retardancy, and directional heat transfer. Therefore, this work offers a design strategy for the preparation of high-performance composite PCMs. The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.
The conversion and storage of photothermal energy using phase change materials (PCMs) represent an optimal approach for harnessing clean and sustainable solar energy. Herein, we encapsulated polyethylene glycol (PEG) in montmorillonite aerogels (3D-Mt) through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs. When used as a support matrix, 3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG. Simultaneously, 3D-Mt/PEG demonstrates outstanding shape retention, increased thermal energy storage density, and commendable thermal and chemical stability. The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating–cooling cycles. Furthermore, the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels, facilitating efficient phonon transfer. This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction. This study addresses the shortcomings of PCMs, including the issues of leakage and inadequate flame retardancy. It achieves the development and design of 3D-Mt/PEG with ultrahigh strength, superior flame retardancy, and directional heat transfer. Therefore, this work offers a design strategy for the preparation of high-performance composite PCMs. The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.
2024, vol. 31, no. 5, pp.
917-928.
https://doi.org/10.1007/s12613-024-2822-y
Abstract:
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
2024, vol. 31, no. 5, pp.
929-942.
https://doi.org/10.1007/s12613-024-2833-8
Abstract:
In recent years, the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased. Local deformation of mining coal-rock results in frequent rockbursts. This has become a critical issue that affects the safe mining of deep, steeply inclined coal seams. In this work, we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data. We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof, explaining the mechanical response behavior of key disaster-prone zones within the deep working face, affected by the dynamics of deep mining. By exploring the spatial correlation inherent in extensive microseismic data, we delineate the “time–space” response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face. The results disclose that (1) the distinctive coal-rock occurrence structure characterized by a “sandwiched rock pillar-B6 roof” constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine, with both elements presenting different degrees of deformation localization with increasing mining depth. (2) As mining depth increases, the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration. The localized deformation of deep, steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions, increasing the energy distribution disparity and stress asymmetry of the “sandwiched rock pillar-B3+6 coal seam-B6 roof” configuration. This makes worse the propensity for frequent dynamic disasters in the working face. (3) The developed high-energy distortion zone “inner–outer” control technology effectively reduces high stress concentration and energy distortion in the surrounding rock. After implementation, the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430% and 300%, respectively, thus guaranteeing the safe and efficient development of steeply inclined coal seams.
In recent years, the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased. Local deformation of mining coal-rock results in frequent rockbursts. This has become a critical issue that affects the safe mining of deep, steeply inclined coal seams. In this work, we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data. We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof, explaining the mechanical response behavior of key disaster-prone zones within the deep working face, affected by the dynamics of deep mining. By exploring the spatial correlation inherent in extensive microseismic data, we delineate the “time–space” response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face. The results disclose that (1) the distinctive coal-rock occurrence structure characterized by a “sandwiched rock pillar-B6 roof” constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine, with both elements presenting different degrees of deformation localization with increasing mining depth. (2) As mining depth increases, the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration. The localized deformation of deep, steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions, increasing the energy distribution disparity and stress asymmetry of the “sandwiched rock pillar-B3+6 coal seam-B6 roof” configuration. This makes worse the propensity for frequent dynamic disasters in the working face. (3) The developed high-energy distortion zone “inner–outer” control technology effectively reduces high stress concentration and energy distortion in the surrounding rock. After implementation, the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430% and 300%, respectively, thus guaranteeing the safe and efficient development of steeply inclined coal seams.
2024, vol. 31, no. 5, pp.
943-958.
https://doi.org/10.1007/s12613-023-2786-3
Abstract:
Flocculation flotation is the most efficient method for recovering fine-grained minerals, and its essence lies in flotation and recovery of flocs. Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure (density and morphology). Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment. However, the influence of floc characteristics on flotation has not been widely studied. Based on the floc formation and flocculation flotation, this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure, summarizing the interaction between floc particle size and structure. Moreover, it thoroughly discusses the effect of floc particle size and structure on floc floatability, further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles. Thus, it is observed that floc particle size is not the only factor influencing flocculation flotation. Within the appropriate apparent particle size range, flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation, thereby resulting in enhanced flotation performance. This study aims to provide a reference for flocculation flotation, targeting the development of more efficient and refined flocculation flotation processes in the future.
Flocculation flotation is the most efficient method for recovering fine-grained minerals, and its essence lies in flotation and recovery of flocs. Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure (density and morphology). Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment. However, the influence of floc characteristics on flotation has not been widely studied. Based on the floc formation and flocculation flotation, this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure, summarizing the interaction between floc particle size and structure. Moreover, it thoroughly discusses the effect of floc particle size and structure on floc floatability, further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles. Thus, it is observed that floc particle size is not the only factor influencing flocculation flotation. Within the appropriate apparent particle size range, flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation, thereby resulting in enhanced flotation performance. This study aims to provide a reference for flocculation flotation, targeting the development of more efficient and refined flocculation flotation processes in the future.
2024, vol. 31, no. 5, pp.
959-976.
https://doi.org/10.1007/s12613-024-2854-3
Abstract:
Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO2 emissions in the ironmaking process. However, hydrogen-enriched reduction produces large amounts of H2O, which places new demands on coke quality in a blast furnace. In a hydrogen-rich blast furnace, the presence of H2O promotes the solution loss reaction. This result improves the reactivity of coke, which is 20%–30% higher in a pure H2O atmosphere than in a pure CO2 atmosphere. The activation energy range is 110–300 kJ/mol between coke and CO2 and 80–170 kJ/mol between coke and H2O. CO2 and H2O are shown to have different effects on coke degradation mechanisms. This review provides a comprehensive overview of the effect of H2O on the structure and properties of coke. By exploring the interactions between H2O and coke, several unresolved issues in the field requiring further research were identified. This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.
Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO2 emissions in the ironmaking process. However, hydrogen-enriched reduction produces large amounts of H2O, which places new demands on coke quality in a blast furnace. In a hydrogen-rich blast furnace, the presence of H2O promotes the solution loss reaction. This result improves the reactivity of coke, which is 20%–30% higher in a pure H2O atmosphere than in a pure CO2 atmosphere. The activation energy range is 110–300 kJ/mol between coke and CO2 and 80–170 kJ/mol between coke and H2O. CO2 and H2O are shown to have different effects on coke degradation mechanisms. This review provides a comprehensive overview of the effect of H2O on the structure and properties of coke. By exploring the interactions between H2O and coke, several unresolved issues in the field requiring further research were identified. This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.
2024, vol. 31, no. 5, pp.
977-987.
https://doi.org/10.1007/s12613-023-2817-0
Abstract:
To investigate the dissolution behaviors of Al2O3 inclusions in CaO–5wt%MgO–SiO2–30wt%Al2O3–TiO2 system ladle slags, confocal scanning laser microscopy was conducted on the slags with different TiO2 contents (0–10wt%), and scanning electron microscopy was performed to study the interfacial reaction between Al2O3 and this slag system. The results disclose that the dissolution of Al2O3 inclusions does not result in the formation of new phases at the boundary between the slag and the inclusions. In TiO2-bearing and TiO2-free ladle slags, there is no difference in the dissolution mechanism of Al2O3 inclusions at steelmaking temperatures. Boundary layer diffusion is found as the controlling step of the dissolution of Al2O3, and the diffusion coefficient is in the range of 4.18 × 10−10 to 2.18 × 10−9 m2/s at 1450–1500°C. Compared with the solubility of Al2O3 in the slags, slag viscosity and temperature play a more profound role in the dissolution of Al2O3 inclusions. A lower viscosity and a lower melting point of the slags are beneficial for the dissolution. Suitable addition of TiO2 (e.g., 5wt%) in ladle slags can enhance the dissolution of Al2O3 inclusions because of the low viscosity and melting point of the slags, while excessive addition of TiO2 (e.g., 10wt%) shows the opposite trend.
To investigate the dissolution behaviors of Al2O3 inclusions in CaO–5wt%MgO–SiO2–30wt%Al2O3–TiO2 system ladle slags, confocal scanning laser microscopy was conducted on the slags with different TiO2 contents (0–10wt%), and scanning electron microscopy was performed to study the interfacial reaction between Al2O3 and this slag system. The results disclose that the dissolution of Al2O3 inclusions does not result in the formation of new phases at the boundary between the slag and the inclusions. In TiO2-bearing and TiO2-free ladle slags, there is no difference in the dissolution mechanism of Al2O3 inclusions at steelmaking temperatures. Boundary layer diffusion is found as the controlling step of the dissolution of Al2O3, and the diffusion coefficient is in the range of 4.18 × 10−10 to 2.18 × 10−9 m2/s at 1450–1500°C. Compared with the solubility of Al2O3 in the slags, slag viscosity and temperature play a more profound role in the dissolution of Al2O3 inclusions. A lower viscosity and a lower melting point of the slags are beneficial for the dissolution. Suitable addition of TiO2 (e.g., 5wt%) in ladle slags can enhance the dissolution of Al2O3 inclusions because of the low viscosity and melting point of the slags, while excessive addition of TiO2 (e.g., 10wt%) shows the opposite trend.
2024, vol. 31, no. 5, pp.
988-1002.
https://doi.org/10.1007/s12613-023-2766-7
Abstract:
Herein, a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was developed. The model provides explicit forms of the activity coefficient of solutes in liquid steel, eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation equilibria. The elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches, such as computational fluid dynamics. The model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing code. The proposed thermodynamic model was developed using a quasichemical approach with two key approximations: random mixing of metallic elements (Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest neighbors. Through these approximations, the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate programs. The model was successfully applied in the calculation of deoxidation equilibria of various elements (Al, B, C, Ca, Ce, Cr, La, Mg, Mn, Nb, Si, Ti, V, and Zr). The limitations of the model arising from these assumptions were also discussed.
Herein, a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was developed. The model provides explicit forms of the activity coefficient of solutes in liquid steel, eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation equilibria. The elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches, such as computational fluid dynamics. The model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing code. The proposed thermodynamic model was developed using a quasichemical approach with two key approximations: random mixing of metallic elements (Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest neighbors. Through these approximations, the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate programs. The model was successfully applied in the calculation of deoxidation equilibria of various elements (Al, B, C, Ca, Ce, Cr, La, Mg, Mn, Nb, Si, Ti, V, and Zr). The limitations of the model arising from these assumptions were also discussed.
2024, vol. 31, no. 5, pp.
1003-1015.
https://doi.org/10.1007/s12613-023-2798-z
Abstract:
Occasional irregular initial solidification phenomena, including stickers, deep oscillation marks, depressions, and surface cracks of strand shells in continuous casting molds, are important limitations for developing the high-efficiency continuous casting of steels. The application of mold thermal monitoring (MTM) systems, which use thermocouples to detect and respond to temperature variations in molds, has become an effective method to address irregular initial solidification phenomena. Such systems are widely applied in numerous steel companies for sticker breakout prediction. However, monitoring the surface defects of strands remains immature. Hence, in-depth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems. This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems. Furthermore, the influences of mold slag behavior on monitoring these phenomena are analyzed. Finally, the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed, and future research directions are proposed.
Occasional irregular initial solidification phenomena, including stickers, deep oscillation marks, depressions, and surface cracks of strand shells in continuous casting molds, are important limitations for developing the high-efficiency continuous casting of steels. The application of mold thermal monitoring (MTM) systems, which use thermocouples to detect and respond to temperature variations in molds, has become an effective method to address irregular initial solidification phenomena. Such systems are widely applied in numerous steel companies for sticker breakout prediction. However, monitoring the surface defects of strands remains immature. Hence, in-depth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems. This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems. Furthermore, the influences of mold slag behavior on monitoring these phenomena are analyzed. Finally, the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed, and future research directions are proposed.
2024, vol. 31, no. 5, pp.
1016-1025.
https://doi.org/10.1007/s12613-023-2763-x
Abstract:
The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m2. Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 μm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.
The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m2. Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 μm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.
2024, vol. 31, no. 5, pp.
1026-1036.
https://doi.org/10.1007/s12613-023-2780-9
Abstract:
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
2024, vol. 31, no. 5, pp.
1037-1047.
https://doi.org/10.1007/s12613-023-2760-0
Abstract:
The infamous type IV failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants. In this work, the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling, i.e., normalizing, cold rolling, and tempering (NCT), which was developed to improve the creep strength of the FGHAZ in G115 steel weldments. The NCT treatment effectively promoted the dissolution of preformed M23C6 particles and relieved the boundary segregation of C and Cr during welding thermal cycling, which accelerated the dispersed reprecipitation of M23C6 particles within the fresh reaustenitized grains during post-weld heat treatment. In addition, the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations. As a result, the interacting actions between precipitates, dislocations, and boundaries during creep were reinforced considerably. Following this strategy, the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%, which can further push the application of G115 steel in USC power plants.
The infamous type IV failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants. In this work, the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling, i.e., normalizing, cold rolling, and tempering (NCT), which was developed to improve the creep strength of the FGHAZ in G115 steel weldments. The NCT treatment effectively promoted the dissolution of preformed M23C6 particles and relieved the boundary segregation of C and Cr during welding thermal cycling, which accelerated the dispersed reprecipitation of M23C6 particles within the fresh reaustenitized grains during post-weld heat treatment. In addition, the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations. As a result, the interacting actions between precipitates, dislocations, and boundaries during creep were reinforced considerably. Following this strategy, the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%, which can further push the application of G115 steel in USC power plants.
2024, vol. 31, no. 5, pp.
1048-1071.
https://doi.org/10.1007/s12613-023-2731-5
Abstract:
The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the molds industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have attracted more and more attention. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.
The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the molds industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have attracted more and more attention. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.
2024, vol. 31, no. 5, pp.
1072-1088.
https://doi.org/10.1007/s12613-024-2869-9
Abstract:
Nickel-based superalloys are extensively used in the crucial hot-section components of industrial gas turbines, aeronautics, and astronautics because of their excellent mechanical properties and corrosion resistance at high temperatures. Fusion welding serves as an effective means for joining and repairing these alloys; however, fusion welding-induced liquation cracking has been a challenging issue. This paper comprehensively reviewed recent liquation cracking, discussing the formation mechanisms, cracking criteria, and remedies. In recent investigations, regulating material composition, changing the preweld heat treatment of the base metal, optimizing the welding process parameters, and applying auxiliary control methods are effective strategies for mitigating cracks. To promote the application of nickel-based superalloys, further research on the combination impact of multiple elements on cracking prevention and specific quantitative criteria for liquation cracking is necessary.
Nickel-based superalloys are extensively used in the crucial hot-section components of industrial gas turbines, aeronautics, and astronautics because of their excellent mechanical properties and corrosion resistance at high temperatures. Fusion welding serves as an effective means for joining and repairing these alloys; however, fusion welding-induced liquation cracking has been a challenging issue. This paper comprehensively reviewed recent liquation cracking, discussing the formation mechanisms, cracking criteria, and remedies. In recent investigations, regulating material composition, changing the preweld heat treatment of the base metal, optimizing the welding process parameters, and applying auxiliary control methods are effective strategies for mitigating cracks. To promote the application of nickel-based superalloys, further research on the combination impact of multiple elements on cracking prevention and specific quantitative criteria for liquation cracking is necessary.
2024, vol. 31, no. 5, pp.
1089-1097.
https://doi.org/10.1007/s12613-023-2792-5
Abstract:
The microstructure characteristics and strengthening mechanism of Inconel738LC (IN-738LC) alloy prepared by using induction-assisted directed energy deposition (IDED) were elucidated through the investigation of samples subjected to IDED under 1050°C preheating with and without hot isostatic pressing (HIP, 1190°C, 105 MPa, and 3 h). Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ' phases in interdendritic and dendritic core regions. After HIP, grain morphology changed negligibly, whereas the size of the γ' phase became increasingly even. After further heat treatment (HT, 1070°C, 2 h + 845°C, 24 h), the γ' phase in the as-deposited and HIPed samples presented a bimodal size distribution, whereas that in the as-deposited sample showed a size that remained uneven. The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%, respectively, due to the synergistic deformation of bimodal γ' phases, especially large cubic γ' phases. Finally, the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.
The microstructure characteristics and strengthening mechanism of Inconel738LC (IN-738LC) alloy prepared by using induction-assisted directed energy deposition (IDED) were elucidated through the investigation of samples subjected to IDED under 1050°C preheating with and without hot isostatic pressing (HIP, 1190°C, 105 MPa, and 3 h). Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ' phases in interdendritic and dendritic core regions. After HIP, grain morphology changed negligibly, whereas the size of the γ' phase became increasingly even. After further heat treatment (HT, 1070°C, 2 h + 845°C, 24 h), the γ' phase in the as-deposited and HIPed samples presented a bimodal size distribution, whereas that in the as-deposited sample showed a size that remained uneven. The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%, respectively, due to the synergistic deformation of bimodal γ' phases, especially large cubic γ' phases. Finally, the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.
2024, vol. 31, no. 5, pp.
1098-1114.
https://doi.org/10.1007/s12613-024-2841-8
Abstract:
Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties, and the microalloying strategy is the most frequently adopted method for such a purpose. In this paper, recent advances in length-scale-dependent scandium (Sc) microalloying effects in Al–Cu model alloys are reviewed. In coarse-grained Al–Cu alloys, the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al2Cu/matrix interface that reduces interfacial energy contribute significantly to θ′ precipitation. By grain size refinement to the fine/ultrafine-grained scale, the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries, promoting the desired intragranular θ′ precipitation. At nanocrystalline scale, the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu, Sc, vacancy)-rich atomic complexes with high thermal stability, outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation. This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.
Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties, and the microalloying strategy is the most frequently adopted method for such a purpose. In this paper, recent advances in length-scale-dependent scandium (Sc) microalloying effects in Al–Cu model alloys are reviewed. In coarse-grained Al–Cu alloys, the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al2Cu/matrix interface that reduces interfacial energy contribute significantly to θ′ precipitation. By grain size refinement to the fine/ultrafine-grained scale, the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries, promoting the desired intragranular θ′ precipitation. At nanocrystalline scale, the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu, Sc, vacancy)-rich atomic complexes with high thermal stability, outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation. This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.
2024, vol. 31, no. 5, pp.
1115-1125.
https://doi.org/10.1007/s12613-024-2827-6
Abstract:
The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial–torsional cyclic tests controlled by stress with various loading paths at room temperature (RT). The evolutionary characteristics and path dependence of multiaxial ratchetting were discussed. Results illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths; multiaxial ratchetting presents strong path dependence, and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional 45° linear loading paths; multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress increase. Moreover, stress–strain curves show a convex and symmetrical shape in axial/torsional directions. Multiaxial ratchetting exhibits quasi-shakedown after certain loading cycles. The abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.
The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial–torsional cyclic tests controlled by stress with various loading paths at room temperature (RT). The evolutionary characteristics and path dependence of multiaxial ratchetting were discussed. Results illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths; multiaxial ratchetting presents strong path dependence, and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional 45° linear loading paths; multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress increase. Moreover, stress–strain curves show a convex and symmetrical shape in axial/torsional directions. Multiaxial ratchetting exhibits quasi-shakedown after certain loading cycles. The abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.
2024, vol. 31, no. 5, pp.
1126-1146.
https://doi.org/10.1007/s12613-024-2862-3
Abstract:
Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer, thereby improving photoelectrochemical performance. Recently, considerable efforts have been devoted to this endeavor. This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms, focusing on the modulation of built-in electric fields in terms of depth and orderliness. First, mechanisms and tuning strategies for built-in electric fields are explored. Then, the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth. Finally, current strategies for constructing bulk built-in electric fields in photoelectrodes are explored, and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.
Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer, thereby improving photoelectrochemical performance. Recently, considerable efforts have been devoted to this endeavor. This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms, focusing on the modulation of built-in electric fields in terms of depth and orderliness. First, mechanisms and tuning strategies for built-in electric fields are explored. Then, the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth. Finally, current strategies for constructing bulk built-in electric fields in photoelectrodes are explored, and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.
2024, vol. 31, no. 5, pp.
1147-1165.
https://doi.org/10.1007/s12613-024-2853-4
Abstract:
The A2B2O7-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.
The A2B2O7-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.
Submit Manuscript
E-mail alert
RSS
