Search2023 Vol. 30, No. 4
Display Method:
2023, vol. 30, no. 4, pp.
601-610.
https://doi.org/10.1007/s12613-022-2539-8
Abstract:
To solve low efficiency, environmental pollution, and toxicity for synthesizing zeolitic imidazolate frameworks (ZIFs) in organic solvents, a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons, which are used as precursors to prepare bimetallic selenide and N-doped carbon (NC) composites. Among them, Fe–Co–Se/NC retains the three-dimensional (3D) polyhedrons with mesoporous structure, and Fe–Co–Se nanoparticles are uniform in size and evenly distributed. When assessed as anode material for lithium-ion batteries, Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 mAh·g−1 at 1.0 A·g−1, and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 mAh·g−1 after 550 cycles. It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites, the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte, and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.
To solve low efficiency, environmental pollution, and toxicity for synthesizing zeolitic imidazolate frameworks (ZIFs) in organic solvents, a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons, which are used as precursors to prepare bimetallic selenide and N-doped carbon (NC) composites. Among them, Fe–Co–Se/NC retains the three-dimensional (3D) polyhedrons with mesoporous structure, and Fe–Co–Se nanoparticles are uniform in size and evenly distributed. When assessed as anode material for lithium-ion batteries, Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 mAh·g−1 at 1.0 A·g−1, and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 mAh·g−1 after 550 cycles. It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites, the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte, and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.
2023, vol. 30, no. 4, pp.
611-620.
https://doi.org/10.1007/s12613-022-2532-2
Abstract:
The Li2ZnTi3O8@LiAlO2 was synthesized by a facile high-temperature solid-state route. The LiAlO2 modification does not alter the morphology and particle size of Li2ZnTi3O8 (LZTO). The LiAlO2 modification improves the structure stability, intercalation/deintercalation reversibility of lithium-ions, and electrochemical reaction activity of Li2ZnTi3O8, and promotes the transfer of lithium ions. Benefited from the unique component, Li2ZnTi3O8@LiAlO2 (8wt%) shows a good rate performance with charge capacities of 203.9, 194.8, 187.4, 180.6, and 177.1 mAh·g−1 at 0.5, 1, 2, 3, and 5 C, respectively. Nevertheless, pure LZTO only delivers charge capacities of 134.5, 109.7, 89.4, 79.9, and 72.9 mAh·g−1 at the corresponding rates. Even at large charge–discharge rate, the Li2ZnTi3O8@LiAlO2 (8wt%) composite indicates a good cycle performance with a high reversible charge/discharge capacity of 263.5/265.8 mAh·g−1 at 5 C after 150 cycles. The introduction of LiAlO2 on the surface of Li2ZnTi3O8 enhances electronic conductivity of the composite, resulting in the good electrochemical performance of Li2ZnTi3O8@LiAlO2 composite. Li2ZnTi3O8@LiAlO2 (8wt%) composite shows a good potential as an anode material for the next generation of high-performance Li-ion batteries.
The Li2ZnTi3O8@LiAlO2 was synthesized by a facile high-temperature solid-state route. The LiAlO2 modification does not alter the morphology and particle size of Li2ZnTi3O8 (LZTO). The LiAlO2 modification improves the structure stability, intercalation/deintercalation reversibility of lithium-ions, and electrochemical reaction activity of Li2ZnTi3O8, and promotes the transfer of lithium ions. Benefited from the unique component, Li2ZnTi3O8@LiAlO2 (8wt%) shows a good rate performance with charge capacities of 203.9, 194.8, 187.4, 180.6, and 177.1 mAh·g−1 at 0.5, 1, 2, 3, and 5 C, respectively. Nevertheless, pure LZTO only delivers charge capacities of 134.5, 109.7, 89.4, 79.9, and 72.9 mAh·g−1 at the corresponding rates. Even at large charge–discharge rate, the Li2ZnTi3O8@LiAlO2 (8wt%) composite indicates a good cycle performance with a high reversible charge/discharge capacity of 263.5/265.8 mAh·g−1 at 5 C after 150 cycles. The introduction of LiAlO2 on the surface of Li2ZnTi3O8 enhances electronic conductivity of the composite, resulting in the good electrochemical performance of Li2ZnTi3O8@LiAlO2 composite. Li2ZnTi3O8@LiAlO2 (8wt%) composite shows a good potential as an anode material for the next generation of high-performance Li-ion batteries.
2023, vol. 30, no. 4, pp.
621-629.
https://doi.org/10.1007/s12613-022-2525-1
Abstract:
Aqueous zinc batteries with low cost and inherent safety are considered to be the most promising energy storage devices. However, they suffer from poor cycling stability and low coulombic efficiencies caused by the adverse zinc dendrites on the anodes during the discharging/charging processes. Chitosan is a kind of natural amino polysaccharide, which is rich in nitrogen and carbon. When sintered at high temperatures, carbon membranes have been achieved with excellent conductivity and graphitization degree, which could enhance the ability to induce zinc ion uniform deposition to some extent. In this work, a type of carbon membrane using chitosan as raw materials has been fabricated by sintering, and then assembled as the protect layers in aqueous zinc batteries. The results show that the samples could retain smoother surfaces when adopting the sintering temperature of 800°C, and the assembled batteries are able to achieve about 700 h at a current density of 0.25 mA·cm−2, which is far longer than those of the similar batteries without any carbon membranes.
Aqueous zinc batteries with low cost and inherent safety are considered to be the most promising energy storage devices. However, they suffer from poor cycling stability and low coulombic efficiencies caused by the adverse zinc dendrites on the anodes during the discharging/charging processes. Chitosan is a kind of natural amino polysaccharide, which is rich in nitrogen and carbon. When sintered at high temperatures, carbon membranes have been achieved with excellent conductivity and graphitization degree, which could enhance the ability to induce zinc ion uniform deposition to some extent. In this work, a type of carbon membrane using chitosan as raw materials has been fabricated by sintering, and then assembled as the protect layers in aqueous zinc batteries. The results show that the samples could retain smoother surfaces when adopting the sintering temperature of 800°C, and the assembled batteries are able to achieve about 700 h at a current density of 0.25 mA·cm−2, which is far longer than those of the similar batteries without any carbon membranes.
2023, vol. 30, no. 4, pp.
630-641.
https://doi.org/10.1007/s12613-022-2559-4
Abstract:
Metal-organic frameworks (MOFs)-based composites have been widely applied as photocatalysts because of their synergistic effect between the two individual component. Herein, TiO2@NH2-MIL-125(Ti) nanocomposites which possess unsaturated titanium–oxo clusters, mesoporous structure, and intimate interface were successfully constructed via an in-situ distilled water-etched route. The X-ray photoelectron spectroscopy (XPS) measurements indicated strong electronic interaction between TiO2 and NH2-MIL-125(Ti), confirming the formation of TiO2@NH2-MIL-125(Ti) nanocomposite. Photoelectrochemical and thermodynamics measurements showed that TiO2@NH2-MIL-125(Ti) nanocomposites have improved charge separation efficient and decreased transfer resistance of the carriers within the heterojunction interfaces, which facilitates the photoexcited electrons transfer and reduction of the Cr(VI) species. Therefore, the optimal TiO2@NH2-MIL-125(Ti) nanocomposite demonstrated superior performance compared to NH2-MIL-125(Ti) and NH2-MIL-125(Ti) derived TiO2. Based on the free radical trapping experiment and electron paramagnetic resonance (EPR) measurements, a possible type-II scheme was proposed for the enhanced photocatalytic activity over the TiO2@NH2-MIL-125(Ti) nanocomposite.
Metal-organic frameworks (MOFs)-based composites have been widely applied as photocatalysts because of their synergistic effect between the two individual component. Herein, TiO2@NH2-MIL-125(Ti) nanocomposites which possess unsaturated titanium–oxo clusters, mesoporous structure, and intimate interface were successfully constructed via an in-situ distilled water-etched route. The X-ray photoelectron spectroscopy (XPS) measurements indicated strong electronic interaction between TiO2 and NH2-MIL-125(Ti), confirming the formation of TiO2@NH2-MIL-125(Ti) nanocomposite. Photoelectrochemical and thermodynamics measurements showed that TiO2@NH2-MIL-125(Ti) nanocomposites have improved charge separation efficient and decreased transfer resistance of the carriers within the heterojunction interfaces, which facilitates the photoexcited electrons transfer and reduction of the Cr(VI) species. Therefore, the optimal TiO2@NH2-MIL-125(Ti) nanocomposite demonstrated superior performance compared to NH2-MIL-125(Ti) and NH2-MIL-125(Ti) derived TiO2. Based on the free radical trapping experiment and electron paramagnetic resonance (EPR) measurements, a possible type-II scheme was proposed for the enhanced photocatalytic activity over the TiO2@NH2-MIL-125(Ti) nanocomposite.
2023, vol. 30, no. 4, pp.
642-652.
https://doi.org/10.1007/s12613-021-2348-5
Abstract:
This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3. A series of SmxMn0.3−xTi catalysts (x = 0, 0.1, 0.15, 0.2, and 0.3) were prepared by co-precipitation. Activity tests indicated that the Sm0.15Mn0.15Ti catalyst showed superior performances, with a NO conversion of 100% and N2 selectivity above 87% at 180–300°C. The characterizations showed that Sm doping suppressed the crystallization of TiO2 and Mn2O3 phases and increased the specific surface area and acidity. In particular, the surface area increased from 152.2 m2·g−1 for Mn0.3Ti to 241.7 m2·g−1 for Sm0.15Mn0.15Ti. These effects contributed to the high catalytic activity. The X-ray photoelectron spectroscopy (XPS) results indicated that the relative atomic ratios of Sm3+/Sm and Oβ/O of Sm0.15Mn0.15Ti were 76.77at% and 44.11at%, respectively. The presence of Sm contributed to an increase in surface-absorbed oxygen (Oβ) and a decrease in Mn4+ surface concentration, which improved the catalytic activity. In the results of hydrogen temperature-programmed reduction (H2-TPR), the presence of Sm induced a higher reduction temperature and lower H2 consumption (0.3 mmol·g−1) for the Sm0.15Mn0.15Ti catalyst compared to the Mn0.3Ti catalyst. The decrease in Mn4+ weakened the redox property of the catalysts and increased the N2 selectivity by suppressing N2O formation from NH3 oxidation and the nonselective catalytic reduction reaction. The in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) revealed that NH3-SCR of NO over the Sm0.15Mn0.15Ti catalyst mainly followed the Eley–Rideal mechanism. Sm doping increased surface-absorbed oxygen and weakened the redox property to improve the NO conversion and N2 selectivity of the Sm0.15Mn0.15Ti catalyst.
This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3. A series of SmxMn0.3−xTi catalysts (x = 0, 0.1, 0.15, 0.2, and 0.3) were prepared by co-precipitation. Activity tests indicated that the Sm0.15Mn0.15Ti catalyst showed superior performances, with a NO conversion of 100% and N2 selectivity above 87% at 180–300°C. The characterizations showed that Sm doping suppressed the crystallization of TiO2 and Mn2O3 phases and increased the specific surface area and acidity. In particular, the surface area increased from 152.2 m2·g−1 for Mn0.3Ti to 241.7 m2·g−1 for Sm0.15Mn0.15Ti. These effects contributed to the high catalytic activity. The X-ray photoelectron spectroscopy (XPS) results indicated that the relative atomic ratios of Sm3+/Sm and Oβ/O of Sm0.15Mn0.15Ti were 76.77at% and 44.11at%, respectively. The presence of Sm contributed to an increase in surface-absorbed oxygen (Oβ) and a decrease in Mn4+ surface concentration, which improved the catalytic activity. In the results of hydrogen temperature-programmed reduction (H2-TPR), the presence of Sm induced a higher reduction temperature and lower H2 consumption (0.3 mmol·g−1) for the Sm0.15Mn0.15Ti catalyst compared to the Mn0.3Ti catalyst. The decrease in Mn4+ weakened the redox property of the catalysts and increased the N2 selectivity by suppressing N2O formation from NH3 oxidation and the nonselective catalytic reduction reaction. The in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) revealed that NH3-SCR of NO over the Sm0.15Mn0.15Ti catalyst mainly followed the Eley–Rideal mechanism. Sm doping increased surface-absorbed oxygen and weakened the redox property to improve the NO conversion and N2 selectivity of the Sm0.15Mn0.15Ti catalyst.
Corrosion resistance and electrical conductivity of V/Ce conversion coating on magnesium alloy AZ31B
2023, vol. 30, no. 4, pp.
653-659.
https://doi.org/10.1007/s12613-022-2463-y
Abstract:
A V/Ce conversion coating was deposited in the surface of AZ31B magnesium alloy in a solution containing vanadate and cerium nitrate. The coating composition and morphology were examined. The conversion coating appears to consist of a thin and cracked coating with a scattering of spherical particles. The corrosion behavior of the substrate and conversion coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Compared with AZ31B magnesium alloy, the corrosion current density of the conversion coating is decreased by two orders of magnitude. The total impedance of the V/Ce conversion coating rise to 1.6 × 103 Ω·cm2 in contrast with 2.2 × 102 Ω·cm2 of the bare AZ31B. In addition, the electrical conductivity of the coating was assessed by conductivity meter and Mott-Schottky measurement. The results reveal a high dependence of the conductivity of the coating on the semiconductor properties of the phase compositions.
A V/Ce conversion coating was deposited in the surface of AZ31B magnesium alloy in a solution containing vanadate and cerium nitrate. The coating composition and morphology were examined. The conversion coating appears to consist of a thin and cracked coating with a scattering of spherical particles. The corrosion behavior of the substrate and conversion coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Compared with AZ31B magnesium alloy, the corrosion current density of the conversion coating is decreased by two orders of magnitude. The total impedance of the V/Ce conversion coating rise to 1.6 × 103 Ω·cm2 in contrast with 2.2 × 102 Ω·cm2 of the bare AZ31B. In addition, the electrical conductivity of the coating was assessed by conductivity meter and Mott-Schottky measurement. The results reveal a high dependence of the conductivity of the coating on the semiconductor properties of the phase compositions.
2023, vol. 30, no. 4, pp.
660-669.
https://doi.org/10.1007/s12613-022-2561-x
Abstract:
The exit-hole in friction stir spot welded (FSSWed) 2024-T4 aluminum alloy joints was successfully repaired by using a three-phase secondary rectification resistance spot welding machine, which is termed as filling exit-hole based on resistance welding (FEBRW). The filling dynamic behavior of force was recorded by a device monitoring. Optical microscope (OM), electron backscatter diffraction (EBSD), and tensile shear tests and finite element modelling were conducted to investigate the repairing stages and bonding mechanisms of the repaired joints in detail. Results showed that exit-hole was completely filled and repaired experiencing three stages. Metallurgical bonding was achieved between plug and exit-hole wall in two forms, including melting bonding in the middle of the joints and partial diffusion bonding on both the upper and bottom of the joints. The highest tensile shear strength of the repaired joints was 7.43 kN, which was 36.3% higher than that of the as welded joints. Resistance welding paves an efficient way to repair the exit-hole in FSSWed joints.
The exit-hole in friction stir spot welded (FSSWed) 2024-T4 aluminum alloy joints was successfully repaired by using a three-phase secondary rectification resistance spot welding machine, which is termed as filling exit-hole based on resistance welding (FEBRW). The filling dynamic behavior of force was recorded by a device monitoring. Optical microscope (OM), electron backscatter diffraction (EBSD), and tensile shear tests and finite element modelling were conducted to investigate the repairing stages and bonding mechanisms of the repaired joints in detail. Results showed that exit-hole was completely filled and repaired experiencing three stages. Metallurgical bonding was achieved between plug and exit-hole wall in two forms, including melting bonding in the middle of the joints and partial diffusion bonding on both the upper and bottom of the joints. The highest tensile shear strength of the repaired joints was 7.43 kN, which was 36.3% higher than that of the as welded joints. Resistance welding paves an efficient way to repair the exit-hole in FSSWed joints.
2023, vol. 30, no. 4, pp.
670-677.
https://doi.org/10.1007/s12613-022-2500-x
Abstract:
This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist. Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher. In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region (FR), while equiaxed grains formed in the deposited region (DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.Besides, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.
This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist. Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher. In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region (FR), while equiaxed grains formed in the deposited region (DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.Besides, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.
2023, vol. 30, no. 4, pp.
678-688.
https://doi.org/10.1007/s12613-022-2543-z
Abstract:
We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al84Ni7Gd6Co3 nanostructured structure. The lattice structure was produced by the selective laser melting and subsequently filled with the Al84Ni7Gd6Co3 amorphous powder, and finally the mixture was used for hot extrusion to produce bulk samples. The results show that the composites achieve a high densification and good interface bonding due to the element diffusion and plastic deformation during hot extrusion. The bulk samples show a heterogeneous structure with a combination of honeycomb lattice structure with an average grain size of less than 1 µm and nanostructured area with a high volume fraction of nanometric intermetallics and nanograin α-Al. The heterogeneous structure leads to a bimodal mechanical zone with hard area and soft area giving rise to high strength and acceptable plasticity, where the compressive yield strength and the compressive plasticity can reach ~745 MPa and ~30%, respectively. The high strength can be explained by the rule of mixture, the grain boundary strengthening, and the back stress, while the acceptable plasticity is mainly owing to the confinement effect of the nanostructured area retarding the brittle fracture behavior.
We report a process route to fabricate an Al–Al interpenetrating-phase composite by combining the Al–Mg–Mn–Sc–Zr lattice structure and Al84Ni7Gd6Co3 nanostructured structure. The lattice structure was produced by the selective laser melting and subsequently filled with the Al84Ni7Gd6Co3 amorphous powder, and finally the mixture was used for hot extrusion to produce bulk samples. The results show that the composites achieve a high densification and good interface bonding due to the element diffusion and plastic deformation during hot extrusion. The bulk samples show a heterogeneous structure with a combination of honeycomb lattice structure with an average grain size of less than 1 µm and nanostructured area with a high volume fraction of nanometric intermetallics and nanograin α-Al. The heterogeneous structure leads to a bimodal mechanical zone with hard area and soft area giving rise to high strength and acceptable plasticity, where the compressive yield strength and the compressive plasticity can reach ~745 MPa and ~30%, respectively. The high strength can be explained by the rule of mixture, the grain boundary strengthening, and the back stress, while the acceptable plasticity is mainly owing to the confinement effect of the nanostructured area retarding the brittle fracture behavior.
2023, vol. 30, no. 4, pp.
689-696.
https://doi.org/10.1007/s12613-022-2513-5
Abstract:
To clarify the correlation of single-crystalline structure with corrosion performance in high-strength TiAl alloys, electrochemical and surface characterization was performed by comparing Ti–45Al–8Nb dual-phase single crystals with their polycrystalline counterparts in NaCl solution. Polarization curves show a lower corrosion rate and a higher pitting potential of ~280 mV for the dual-phase single crystals. Electrochemical impedance spectroscopy and potentiostatic polarization plots revealed a higher impedance of the charge transfer through the compact passive film. Surface composition analysis indicated a compact film with more content of Nb, as twice as that in the film on the polycrystals. Our results reflect that the dual-phase Ti–45Al–8Nb single crystals possess a higher corrosion resistance in NaCl solution, compared with their polycrystalline counterpart, arising from a more homogeneous microstructure and composition distribution.
To clarify the correlation of single-crystalline structure with corrosion performance in high-strength TiAl alloys, electrochemical and surface characterization was performed by comparing Ti–45Al–8Nb dual-phase single crystals with their polycrystalline counterparts in NaCl solution. Polarization curves show a lower corrosion rate and a higher pitting potential of ~280 mV for the dual-phase single crystals. Electrochemical impedance spectroscopy and potentiostatic polarization plots revealed a higher impedance of the charge transfer through the compact passive film. Surface composition analysis indicated a compact film with more content of Nb, as twice as that in the film on the polycrystals. Our results reflect that the dual-phase Ti–45Al–8Nb single crystals possess a higher corrosion resistance in NaCl solution, compared with their polycrystalline counterpart, arising from a more homogeneous microstructure and composition distribution.
2023, vol. 30, no. 4, pp.
697-706.
https://doi.org/10.1007/s12613-021-2371-6
Abstract:
Powder hot isostatic pressing (HIP) is an effective method to achieve near-net-shape manufacturing of high-quality complex thin-walled titanium alloy parts, and it has received extensive attention in recent years. However, there are few reports about the microstructure characteristics on the strengthening and toughening mechanisms of powder hot isostatic pressed (HIPed) titanium alloys. Therefore, TA15 powder was prepared into alloy by HIP approach, which was used to explore the microstructure characteristics at different HIP temperatures and the corresponding tensile properties and fracture toughness. Results show that the fabricated alloy has a “basket-like structure” when the HIP temperature is below 950°C, consisting of lath clusters and surrounding small equiaxed grains belts. When the HIP temperature is higher than 950°C, the microstructure gradually transforms into the Widmanstatten structure, accompanied by a significant increase in grain size. The tensile strength and elongation are reduced from 948 MPa and 17.3% for the 910°C specimen to 861 MPa and 10% for the 970°C specimen. The corresponding tensile fracture mode changes from transcrystalline plastic fracture to mixed fracture including intercrystalline cleavage. The fracture toughness of the specimens increases from 82.64 MPa·m1/2 for the 910°C specimen to 140.18 MPa·m1/2 for the 970°C specimen. Specimens below 950°C tend to form holes due to the prior particle boundaries (PPBs), which is not conducive to toughening. Specimens above 950°C have high fracture toughness due to the crack deflection, crack branching, and shear plastic deformation of the Widmanstatten structure. This study provides a valid reference for the development of powder HIPed titanium alloy.
Powder hot isostatic pressing (HIP) is an effective method to achieve near-net-shape manufacturing of high-quality complex thin-walled titanium alloy parts, and it has received extensive attention in recent years. However, there are few reports about the microstructure characteristics on the strengthening and toughening mechanisms of powder hot isostatic pressed (HIPed) titanium alloys. Therefore, TA15 powder was prepared into alloy by HIP approach, which was used to explore the microstructure characteristics at different HIP temperatures and the corresponding tensile properties and fracture toughness. Results show that the fabricated alloy has a “basket-like structure” when the HIP temperature is below 950°C, consisting of lath clusters and surrounding small equiaxed grains belts. When the HIP temperature is higher than 950°C, the microstructure gradually transforms into the Widmanstatten structure, accompanied by a significant increase in grain size. The tensile strength and elongation are reduced from 948 MPa and 17.3% for the 910°C specimen to 861 MPa and 10% for the 970°C specimen. The corresponding tensile fracture mode changes from transcrystalline plastic fracture to mixed fracture including intercrystalline cleavage. The fracture toughness of the specimens increases from 82.64 MPa·m1/2 for the 910°C specimen to 140.18 MPa·m1/2 for the 970°C specimen. Specimens below 950°C tend to form holes due to the prior particle boundaries (PPBs), which is not conducive to toughening. Specimens above 950°C have high fracture toughness due to the crack deflection, crack branching, and shear plastic deformation of the Widmanstatten structure. This study provides a valid reference for the development of powder HIPed titanium alloy.
2023, vol. 30, no. 4, pp.
707-714.
https://doi.org/10.1007/s12613-022-2567-4
Abstract:
Designing strong, yet ductile, and body-centered cubic (BCC) medium-entropy alloys (MEAs) remains to be a challenge nowadays. In this study, the strength–ductility trade-off of Ni0.6CoFe1.4 MEAs was tackled via introducing a BCC + face-centered cubic (FCC) dual-phase microstructure. Ni0.6CoFe1.4Nbx (x = 0, 0.05, 0.08, 0.10, and 0.15, in molar ratio) MEAs were prepared using vacuum induction melting. Results show that the new alloy is composed of BCC plus FCC dual phases featuring a network-like structure, and the BCC phase is the main phase in this alloy system. Moreover, the Nb0.10 MEA shows high strength and respectable tensile ductility, representing the best combination of the strength and fracture elongation among the alloys studied here. The remarkable strength of the Nb0.10 MEA is attributed to the combined effect of the solid solution strengthening, the precipitation hardening effect and the interface strengthening effect.
Designing strong, yet ductile, and body-centered cubic (BCC) medium-entropy alloys (MEAs) remains to be a challenge nowadays. In this study, the strength–ductility trade-off of Ni0.6CoFe1.4 MEAs was tackled via introducing a BCC + face-centered cubic (FCC) dual-phase microstructure. Ni0.6CoFe1.4Nbx (x = 0, 0.05, 0.08, 0.10, and 0.15, in molar ratio) MEAs were prepared using vacuum induction melting. Results show that the new alloy is composed of BCC plus FCC dual phases featuring a network-like structure, and the BCC phase is the main phase in this alloy system. Moreover, the Nb0.10 MEA shows high strength and respectable tensile ductility, representing the best combination of the strength and fracture elongation among the alloys studied here. The remarkable strength of the Nb0.10 MEA is attributed to the combined effect of the solid solution strengthening, the precipitation hardening effect and the interface strengthening effect.
2023, vol. 30, no. 4, pp.
715-723.
https://doi.org/10.1007/s12613-022-2516-2
Abstract:
The Ni60/15wt% Cu directional structure coating was prepared by the composite technology of flame spraying, induction remelting, and forced cooling, and the effect of Cu on the microstructure, phase, hardness, and wear performance of Ni60 coatings was investigated. Results showed that Cu addition makes the microstructure of Ni60 directional structure coating more compact, and Cu is mainly enriched within the crystal grain, resulting in the formation of Cu3.8Ni as the bonding phase. Compared with Ni60 directional structure coating, Ni60/Cu directional structure coating has a lower hardness, lower friction coefficient, and lower wear rate, which indicate that Cu can effectively enhance the antifriction performance of Ni60 directional structure coating.
The Ni60/15wt% Cu directional structure coating was prepared by the composite technology of flame spraying, induction remelting, and forced cooling, and the effect of Cu on the microstructure, phase, hardness, and wear performance of Ni60 coatings was investigated. Results showed that Cu addition makes the microstructure of Ni60 directional structure coating more compact, and Cu is mainly enriched within the crystal grain, resulting in the formation of Cu3.8Ni as the bonding phase. Compared with Ni60 directional structure coating, Ni60/Cu directional structure coating has a lower hardness, lower friction coefficient, and lower wear rate, which indicate that Cu can effectively enhance the antifriction performance of Ni60 directional structure coating.
2023, vol. 30, no. 4, pp.
724-733.
https://doi.org/10.1007/s12613-022-2434-3
Abstract:
Fusion welding easily causes microstructural coarsening in the heat-affected zone (HAZ) of a thick-gauge pipeline steel joint. This is most significant in the inter-critically coarse-grained HAZ (ICCGHAZ), which considerably deteriorates the toughness of the joint. In the present work, 11-mm thick pipeline steel was joined by preheating and double-sided friction stir welding (FSW). A comparative study on the microstructure and toughness in the ICCGHAZs for FSW and gas metal arc welding (GMAW) was performed. The toughness in the ICCGHAZ for FSW was improved significantly than that in the ICCGHAZ for GMAW. Generally, the nugget zone (NZ) has a coarse microstructure in the FSW steel joint formed at the highest peak temperature. However, in the current study, the microstructure in the one-pass NZ was remarkably refined owing to the static recrystallization of ferrite. An excellent toughness was achieved in the NZ of the pipeline steel joint that employed FSW.
Fusion welding easily causes microstructural coarsening in the heat-affected zone (HAZ) of a thick-gauge pipeline steel joint. This is most significant in the inter-critically coarse-grained HAZ (ICCGHAZ), which considerably deteriorates the toughness of the joint. In the present work, 11-mm thick pipeline steel was joined by preheating and double-sided friction stir welding (FSW). A comparative study on the microstructure and toughness in the ICCGHAZs for FSW and gas metal arc welding (GMAW) was performed. The toughness in the ICCGHAZ for FSW was improved significantly than that in the ICCGHAZ for GMAW. Generally, the nugget zone (NZ) has a coarse microstructure in the FSW steel joint formed at the highest peak temperature. However, in the current study, the microstructure in the one-pass NZ was remarkably refined owing to the static recrystallization of ferrite. An excellent toughness was achieved in the NZ of the pipeline steel joint that employed FSW.
2023, vol. 30, no. 4, pp.
734-743.
https://doi.org/10.1007/s12613-022-2531-3
Abstract:
Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150°C and the strain rate range was 0.01–5 s−1 on a Gleeble-3800 thermal simulator machine. The results showed that the flow stress increased with decreasing deformation temperature and increasing strain rate. According to the constitutive equation, the activation energy of hot deformation was 422.88 kJ·mol−1. The relationship between the critical stress and peak stress of the tested steel was established, and a dynamic recrystallization kinetic model was thus obtained. Based on this model, the effects of strain rate and deformation temperature on the volume fraction of dynamically recrystallized grains were explored. The microstructural examination and processing map results revealed that the tested steel exhibited a good hot workability at deformation temperatures of 1010–1100°C and strain rate of 0.01 s−1.
Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150°C and the strain rate range was 0.01–5 s−1 on a Gleeble-3800 thermal simulator machine. The results showed that the flow stress increased with decreasing deformation temperature and increasing strain rate. According to the constitutive equation, the activation energy of hot deformation was 422.88 kJ·mol−1. The relationship between the critical stress and peak stress of the tested steel was established, and a dynamic recrystallization kinetic model was thus obtained. Based on this model, the effects of strain rate and deformation temperature on the volume fraction of dynamically recrystallized grains were explored. The microstructural examination and processing map results revealed that the tested steel exhibited a good hot workability at deformation temperatures of 1010–1100°C and strain rate of 0.01 s−1.
2023, vol. 30, no. 4, pp.
744-755.
https://doi.org/10.1007/s12613-022-2588-z
Abstract:
CaO–SiO2 compounds compromise one of the most common series of oxide particles in liquid steels, which could significantly affect the service performance of the steels as crack initiation sites. However, the structural, electronic, and mechanical properties of the compounds in CaO–SiO2 system are still not fully clarified due to the difficulties in the experiments. In this study, a thorough investigation of these properties of CaO–SiO2 compound particles in steels was conducted based on first-principles density functional theory. Corresponding phases were determined by thermodynamic calculation, including gamma dicalcium silicate (γ-C2S), alpha-prime (L) dicalcium silicate (\begin{document}${\text α\,}_{\rm{L }}{'} $\end{document} ![]()
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CaO–SiO2 compounds compromise one of the most common series of oxide particles in liquid steels, which could significantly affect the service performance of the steels as crack initiation sites. However, the structural, electronic, and mechanical properties of the compounds in CaO–SiO2 system are still not fully clarified due to the difficulties in the experiments. In this study, a thorough investigation of these properties of CaO–SiO2 compound particles in steels was conducted based on first-principles density functional theory. Corresponding phases were determined by thermodynamic calculation, including gamma dicalcium silicate (γ-C2S), alpha-prime (L) dicalcium silicate (
2023, vol. 30, no. 4, pp.
756-765.
https://doi.org/10.1007/s12613-022-2435-2
Abstract:
Different amounts of AlON have been introduced in calcium hexaaluminate (CA6) using two approaches, that is, one-step and two-step methods, to improve the slag resistance of CA6. A one-step method can directly sinter the mixtures combining Al2O3, CaCO3, and Al in flowing nitrogen, in which AlON clusters are always formed because of the poor wettability of Al by Al2O3, leading to the high porosity of CA6/AlON composite. In a two-step method, CA6 and AlON are prepared separately and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by the one-step method, CA6 and AlON in composite by the two-step method are more uniformly distributed, and the optimized amount of AlON added is 10wt%. The slag corrosion and penetration test shows that the CA6/AlON composite using the two-step method exhibits superior slag corrosion protection. The promoted effect of AlON on slag penetration and corrosion resistance is also discussed.
Different amounts of AlON have been introduced in calcium hexaaluminate (CA6) using two approaches, that is, one-step and two-step methods, to improve the slag resistance of CA6. A one-step method can directly sinter the mixtures combining Al2O3, CaCO3, and Al in flowing nitrogen, in which AlON clusters are always formed because of the poor wettability of Al by Al2O3, leading to the high porosity of CA6/AlON composite. In a two-step method, CA6 and AlON are prepared separately and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by the one-step method, CA6 and AlON in composite by the two-step method are more uniformly distributed, and the optimized amount of AlON added is 10wt%. The slag corrosion and penetration test shows that the CA6/AlON composite using the two-step method exhibits superior slag corrosion protection. The promoted effect of AlON on slag penetration and corrosion resistance is also discussed.
2023, vol. 30, no. 4, pp.
766-771.
https://doi.org/10.1007/s12613-022-2497-1
Abstract:
Periodic nitrogen-doped homoepitaxial nano-multilayers were grown by microwave plasma chemical vapor deposition. The residual time of gases (such as CH4 and N2) in the chamber was determined by optical emission spectroscopy to determine the nano-multilayer growth process, and thin, nanoscale nitrogen-doped layers were obtained. The highest toughness of 18.2 MPa∙m1/2 under a Young’s modulus of 1000 GPa is obtained when the single-layer thickness of periodic nitrogen-doped nano-multilayers is about 96 nm. The fracture toughness of periodic nitrogen-doped CVD layer is about 2.1 times that of the HPHT seed substrate. Alternating tensile and compressive stresses are derived from periodic nitrogen doping; hence, the fracture toughness is significantly improved. Single-crystal diamond with a high toughness demonstrates wide application prospects for high-pressure anvils and single-point diamond cutting tools.
Periodic nitrogen-doped homoepitaxial nano-multilayers were grown by microwave plasma chemical vapor deposition. The residual time of gases (such as CH4 and N2) in the chamber was determined by optical emission spectroscopy to determine the nano-multilayer growth process, and thin, nanoscale nitrogen-doped layers were obtained. The highest toughness of 18.2 MPa∙m1/2 under a Young’s modulus of 1000 GPa is obtained when the single-layer thickness of periodic nitrogen-doped nano-multilayers is about 96 nm. The fracture toughness of periodic nitrogen-doped CVD layer is about 2.1 times that of the HPHT seed substrate. Alternating tensile and compressive stresses are derived from periodic nitrogen doping; hence, the fracture toughness is significantly improved. Single-crystal diamond with a high toughness demonstrates wide application prospects for high-pressure anvils and single-point diamond cutting tools.
2023, vol. 30, no. 4, pp.
772-781.
https://doi.org/10.1007/s12613-022-2565-6
Abstract:
Thermal interface materials (TIMs) play a vital role in the thermal management of electronic devices and can significantly reduce thermal contact resistance (TCR). The TCR between the solid–liquid contact surface is much smaller than that of the solid–solid contact surface, but conventional solid–liquid phase change materials are likely to cause serious leakage. Therefore, this work has prepared a new form-stable phase change thermal interface material. Through the melt blending of paraffin wax (PW) and low-density polyethylene (LDPE), the stability is improved and it has an excellent coating effect on PW. The addition of aluminum (Al) powder improves the low thermal conductivity of PW/LDPE, and the addition of 15wt% Al powder improves the thermal conductivity of the internal structure of the matrix by 67%. In addition, the influence of the addition of Al powder on the internal structure, thermal properties, and phase change behavior of the PW/LDPE matrix was systematically studied. The results confirmed that the addition of Al powder improved the thermal conductivity of the material without a significant impact on other properties, and the thermal conductivity increased with the increase of Al addition. Therefore, morphologically stable PW/LDPE/Al is an important development direction for TIMs.
Thermal interface materials (TIMs) play a vital role in the thermal management of electronic devices and can significantly reduce thermal contact resistance (TCR). The TCR between the solid–liquid contact surface is much smaller than that of the solid–solid contact surface, but conventional solid–liquid phase change materials are likely to cause serious leakage. Therefore, this work has prepared a new form-stable phase change thermal interface material. Through the melt blending of paraffin wax (PW) and low-density polyethylene (LDPE), the stability is improved and it has an excellent coating effect on PW. The addition of aluminum (Al) powder improves the low thermal conductivity of PW/LDPE, and the addition of 15wt% Al powder improves the thermal conductivity of the internal structure of the matrix by 67%. In addition, the influence of the addition of Al powder on the internal structure, thermal properties, and phase change behavior of the PW/LDPE matrix was systematically studied. The results confirmed that the addition of Al powder improved the thermal conductivity of the material without a significant impact on other properties, and the thermal conductivity increased with the increase of Al addition. Therefore, morphologically stable PW/LDPE/Al is an important development direction for TIMs.
2023, vol. 30, no. 4, pp.
782-789.
https://doi.org/10.1007/s12613-022-2502-8
Abstract:
Through systematical experiment design, the physical blowing agent (PBA) mass loss of bio-based polyurethane rigid foam (PURF) in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass losses were measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and this method has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations\begin{document}$ {\sigma }_{1} $\end{document} ![]()
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Through systematical experiment design, the physical blowing agent (PBA) mass loss of bio-based polyurethane rigid foam (PURF) in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass losses were measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and this method has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations
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