Search2018 Vol. 25, No. 8
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2018, vol. 25, no. 8, pp.
849-860.
https://doi.org/10.1007/s12613-018-1634-3
Abstract:
The flotation of hemimorphite using the S(Ⅱ)–Pb(Ⅱ)–xanthate process, which includes sulfidization with sodium sulfide, activation by lead cations, and subsequent flotation with xanthate, was investigated. The flotation results indicated that hemimorphite floats when the S(Ⅱ)–Pb(Ⅱ)–xanthate process is used; a maximum recovery of approximately 90% was obtained. Zeta-potential, contact-angle, scanning electron microscopy–energy-dispersive spectrometry (SEM–EDS), and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to characterize the activation products on the hemimorphite surface and their subsequent interaction with sodium butyl xanthate (SBX). The results showed that a ZnS coating formed on the hemimorphite surface after the sample was conditioned in an Na2S solution. However, the formation of a ZnS coating on the hemimorphite surface did not improve hemimorphite flotation. With the subsequent addition of lead cations, PbS species formed on the mineral surface. The formation of the PbS species on the surface of hemimorphite significantly increased the adsorption capacity of SBX, forming lead xanthate (referred to as chemical adsorption) and leading to a substantial improvement in hemimorphite flotation. Our results indicate that the addition of lead cations is a critical step in the successful flotation of hemimorphite using the sulfidization–lead ion activation–xanthate process.
The flotation of hemimorphite using the S(Ⅱ)–Pb(Ⅱ)–xanthate process, which includes sulfidization with sodium sulfide, activation by lead cations, and subsequent flotation with xanthate, was investigated. The flotation results indicated that hemimorphite floats when the S(Ⅱ)–Pb(Ⅱ)–xanthate process is used; a maximum recovery of approximately 90% was obtained. Zeta-potential, contact-angle, scanning electron microscopy–energy-dispersive spectrometry (SEM–EDS), and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to characterize the activation products on the hemimorphite surface and their subsequent interaction with sodium butyl xanthate (SBX). The results showed that a ZnS coating formed on the hemimorphite surface after the sample was conditioned in an Na2S solution. However, the formation of a ZnS coating on the hemimorphite surface did not improve hemimorphite flotation. With the subsequent addition of lead cations, PbS species formed on the mineral surface. The formation of the PbS species on the surface of hemimorphite significantly increased the adsorption capacity of SBX, forming lead xanthate (referred to as chemical adsorption) and leading to a substantial improvement in hemimorphite flotation. Our results indicate that the addition of lead cations is a critical step in the successful flotation of hemimorphite using the sulfidization–lead ion activation–xanthate process.
2018, vol. 25, no. 8, pp.
861-870.
https://doi.org/10.1007/s12613-018-1635-2
Abstract:
This paper investigates the leaching behavior of heavy metals (V, Pb, Cd, Cr, and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments. The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb, Cd, and Cr were high in the early stage before decreasing. The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions. The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V, Pb, and As decreased in the order fine fraction > medium fraction > coarse fraction, and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction, respectively. The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V (17104.36 μg/kg) > As (609.41 μg/kg) > Pb (469.24 μg/kg) > Cr (56.35 μg/kg) > Cd (27.52 μg/kg), and the dissolution rates decreased in the order As (2.96%) > Pb (0.93%) > V (0.35%) > Cd (0.25%) > Cr (0.01%). The specific surface area, pore size of the stone coal waste rocks, and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks. Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model. The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks.
This paper investigates the leaching behavior of heavy metals (V, Pb, Cd, Cr, and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments. The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb, Cd, and Cr were high in the early stage before decreasing. The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions. The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V, Pb, and As decreased in the order fine fraction > medium fraction > coarse fraction, and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction, respectively. The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V (17104.36 μg/kg) > As (609.41 μg/kg) > Pb (469.24 μg/kg) > Cr (56.35 μg/kg) > Cd (27.52 μg/kg), and the dissolution rates decreased in the order As (2.96%) > Pb (0.93%) > V (0.35%) > Cd (0.25%) > Cr (0.01%). The specific surface area, pore size of the stone coal waste rocks, and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks. Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model. The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks.
2018, vol. 25, no. 8, pp.
871-880.
https://doi.org/10.1007/s12613-018-1636-1
Abstract:
To develop a smelting process for the comprehensive utilization of high-chromium vanadium-titanium magnetite (HCVTM), the micro-sinter test was applied to investigate the influence of basicity and temperature on the HCVTM sinters. The bonding phase strength (BS) was tested via an electronic universal testing machine. The phase transformations of the HCVTM sinters were detected via X-ray diffraction (XRD), whereas the structure and mineralogy of the HCVTM sinters under different temperatures and basicities were detected via scanning electron microscopy in combination with energy-dispersive spectroscopy (SEM–EDS). Our results demonstrate that the BS of the HCVTM sinters exhibits a slightly increasing tendency with an increase in temperature when the basicity is 2.4 and within the range of 2.8–4.0. Many cracks, small size crystals, and dependent phase structures are generated by increasing the sinter basicity. The BS is lower than 4000 N when the basicity is 2.2 and 2.8. When the temperature is in the range of 1280–1300℃, the BS exceeds 4000 N with the basicity of 2.0, 2.4, and 3.4–4.0. The pore size of the HCVTM sinters increases with the increase of the temperature. The perovskite decreases, whereas the silicate phase increases with basicity higher than 3.2. This study provides theoretical and technical foundations for the effective production of HCVTM sinters.
To develop a smelting process for the comprehensive utilization of high-chromium vanadium-titanium magnetite (HCVTM), the micro-sinter test was applied to investigate the influence of basicity and temperature on the HCVTM sinters. The bonding phase strength (BS) was tested via an electronic universal testing machine. The phase transformations of the HCVTM sinters were detected via X-ray diffraction (XRD), whereas the structure and mineralogy of the HCVTM sinters under different temperatures and basicities were detected via scanning electron microscopy in combination with energy-dispersive spectroscopy (SEM–EDS). Our results demonstrate that the BS of the HCVTM sinters exhibits a slightly increasing tendency with an increase in temperature when the basicity is 2.4 and within the range of 2.8–4.0. Many cracks, small size crystals, and dependent phase structures are generated by increasing the sinter basicity. The BS is lower than 4000 N when the basicity is 2.2 and 2.8. When the temperature is in the range of 1280–1300℃, the BS exceeds 4000 N with the basicity of 2.0, 2.4, and 3.4–4.0. The pore size of the HCVTM sinters increases with the increase of the temperature. The perovskite decreases, whereas the silicate phase increases with basicity higher than 3.2. This study provides theoretical and technical foundations for the effective production of HCVTM sinters.
2018, vol. 25, no. 8, pp.
881-891.
https://doi.org/10.1007/s12613-018-1637-0
Abstract:
The slag cleaning (or matte settling) process was experimentally investigated at 1573 K using a fayalitic nickel converter slag containing spinel and matte/alloy particles. The addition of various amounts of spent potlining (SPL) was studied in terms of its influence on matte settling and the overall metal recoveries. The slags produced were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and wet chemical analysis using inductively coupled plasma optical emission spectrometry. The presence of solid spinel particles in the molten slag hindered coalescence and settling of matte/alloy droplets. Matte settling was effectively promoted with the addition of as little as 2wt% SPL because of the reduction of spinel by the carbonaceous component of the SPL. The reduced viscosity of the molten slag in the presence of SPL also contributed to the accelerated matte settling. Greater metal recoveries were achieved with larger amounts of added SPL. Fast reduction of the molten slag at 1573 K promoted the formation of highly dispersed metal particles/clusters via accelerated nucleation in the molten slag, which increased the overall slag viscosity. This increase in viscosity, when combined with rapid gas evolution from accelerated reduction reactions, led to slag foaming.
The slag cleaning (or matte settling) process was experimentally investigated at 1573 K using a fayalitic nickel converter slag containing spinel and matte/alloy particles. The addition of various amounts of spent potlining (SPL) was studied in terms of its influence on matte settling and the overall metal recoveries. The slags produced were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and wet chemical analysis using inductively coupled plasma optical emission spectrometry. The presence of solid spinel particles in the molten slag hindered coalescence and settling of matte/alloy droplets. Matte settling was effectively promoted with the addition of as little as 2wt% SPL because of the reduction of spinel by the carbonaceous component of the SPL. The reduced viscosity of the molten slag in the presence of SPL also contributed to the accelerated matte settling. Greater metal recoveries were achieved with larger amounts of added SPL. Fast reduction of the molten slag at 1573 K promoted the formation of highly dispersed metal particles/clusters via accelerated nucleation in the molten slag, which increased the overall slag viscosity. This increase in viscosity, when combined with rapid gas evolution from accelerated reduction reactions, led to slag foaming.
2018, vol. 25, no. 8, pp.
892-901.
https://doi.org/10.1007/s12613-018-1638-z
Abstract:
The increasing speed of trains necessitates the development of brake-disc materials that meet more stringent requirements. Therefore, Nb and V have been added to Cr–Mo–V steel to improve its thermal fatigue performance when used in brake discs. In this paper, the influences of Nb and V on the static continuous cooling transformation (CCT) behaviors of undercooled austenite were studied. The microstructures, hardness, and dislocation densities at different cooling rates and with the addition of different alloying elements were also investigated. The results show that the transformation products of ferrite, granular bainite, lower bainite, and martensite form under different cooling conditions. With increasing Nb and V contents, the CCT curves are shifted to the left, ferrite and bainite transformations are promoted, and the critical cooling rate of total martensite formation is increased. The added V mainly forms V-rich M8C7 precipitates and reduces the dissolved C content; therefore, the Ac1, Ac3, and Ms-point temperatures increase. Moreover, the stability of retained austenite is also reduced; its content therefore decreases. Compared with V, the effect of added Nb is weaker because of its smaller content. However, the addition of Nb improves the hardness at lower cooling rates because of the precipitation of fine NbC particles and refining of the microstructure.
The increasing speed of trains necessitates the development of brake-disc materials that meet more stringent requirements. Therefore, Nb and V have been added to Cr–Mo–V steel to improve its thermal fatigue performance when used in brake discs. In this paper, the influences of Nb and V on the static continuous cooling transformation (CCT) behaviors of undercooled austenite were studied. The microstructures, hardness, and dislocation densities at different cooling rates and with the addition of different alloying elements were also investigated. The results show that the transformation products of ferrite, granular bainite, lower bainite, and martensite form under different cooling conditions. With increasing Nb and V contents, the CCT curves are shifted to the left, ferrite and bainite transformations are promoted, and the critical cooling rate of total martensite formation is increased. The added V mainly forms V-rich M8C7 precipitates and reduces the dissolved C content; therefore, the Ac1, Ac3, and Ms-point temperatures increase. Moreover, the stability of retained austenite is also reduced; its content therefore decreases. Compared with V, the effect of added Nb is weaker because of its smaller content. However, the addition of Nb improves the hardness at lower cooling rates because of the precipitation of fine NbC particles and refining of the microstructure.
2018, vol. 25, no. 8, pp.
902-912.
https://doi.org/10.1007/s12613-018-1639-y
Abstract:
In the present work, a compressible and lubricating space-holder material commonly known as “acrawax” was used to process Cu foams with various pore sizes and various porosities. The foams were processed without using binders to avoid contamination of their metal matrices. The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder. In addition, the use of acrawax as a space-holder material yielded considerably dense cell walls, which are an essential prerequisite for better material properties. The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder. The isotropic pore shape, uniform pore distribution throughout the metal matrix, and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples. The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.
In the present work, a compressible and lubricating space-holder material commonly known as “acrawax” was used to process Cu foams with various pore sizes and various porosities. The foams were processed without using binders to avoid contamination of their metal matrices. The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder. In addition, the use of acrawax as a space-holder material yielded considerably dense cell walls, which are an essential prerequisite for better material properties. The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder. The isotropic pore shape, uniform pore distribution throughout the metal matrix, and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples. The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.
2018, vol. 25, no. 8, pp.
913-921.
https://doi.org/10.1007/s12613-018-1640-5
Abstract:
The precipitates in P92 steel after long-term service in an ultra-supercritical unit were investigated by field-emission scanning electron microscopy and transmission electron microscopy and were found to mainly consist of M23C6 carbides, Laves phase, and MX carbonitrides. No Z-phase was observed. M23C6 carbides and Laves phase were found not only on prior austenite grain boundaries, martensite lath boundaries, and subgrain boundaries but also in lath interiors, where two types of MX carbonitrides—Nb-rich and V-rich particles—were also observed but the “winged” complexes were hardly found. Each kind of precipitate within the martensite laths exhibited multifarious morphologies, suggesting that a morphological change of precipitates occurred during long-term service. The M23C6 carbides and Laves phase coarsened substantially, and the latter grew faster than the former. However, MX carbonitrides exhibited a relatively low coarsening rate. The effect of the evolution of the precipitate phases on the creep rupture strength of P92 steel was discussed.
The precipitates in P92 steel after long-term service in an ultra-supercritical unit were investigated by field-emission scanning electron microscopy and transmission electron microscopy and were found to mainly consist of M23C6 carbides, Laves phase, and MX carbonitrides. No Z-phase was observed. M23C6 carbides and Laves phase were found not only on prior austenite grain boundaries, martensite lath boundaries, and subgrain boundaries but also in lath interiors, where two types of MX carbonitrides—Nb-rich and V-rich particles—were also observed but the “winged” complexes were hardly found. Each kind of precipitate within the martensite laths exhibited multifarious morphologies, suggesting that a morphological change of precipitates occurred during long-term service. The M23C6 carbides and Laves phase coarsened substantially, and the latter grew faster than the former. However, MX carbonitrides exhibited a relatively low coarsening rate. The effect of the evolution of the precipitate phases on the creep rupture strength of P92 steel was discussed.
2018, vol. 25, no. 8, pp.
922-929.
https://doi.org/10.1007/s12613-018-1641-4
Abstract:
18Mn18Cr0.5N steel with an initial grain size of 28–177 μm was processed by 2.5%–20% cold rolling and annealing at 1000℃ for 24 h, and the grain boundary character distribution was examined via electron backscatter diffraction. Low strain (2.5%) favored the formation of low-Σ boundaries. At this strain, the fraction of low-Σ boundaries was insensitive to the initial grain size. However, specimens with fine initial grains showed decreasing grain size after grain boundary engineering processing. The fraction of low-Σ boundaries and the (Σ9 + Σ27)/Σ3 value decreased with increasing strain; furthermore, the specimens with fine initial grain size were sensitive to the strain. Finally, the effects of the initial grain size and strain on the grain boundary engineering were discussed in detail.
18Mn18Cr0.5N steel with an initial grain size of 28–177 μm was processed by 2.5%–20% cold rolling and annealing at 1000℃ for 24 h, and the grain boundary character distribution was examined via electron backscatter diffraction. Low strain (2.5%) favored the formation of low-Σ boundaries. At this strain, the fraction of low-Σ boundaries was insensitive to the initial grain size. However, specimens with fine initial grains showed decreasing grain size after grain boundary engineering processing. The fraction of low-Σ boundaries and the (Σ9 + Σ27)/Σ3 value decreased with increasing strain; furthermore, the specimens with fine initial grain size were sensitive to the strain. Finally, the effects of the initial grain size and strain on the grain boundary engineering were discussed in detail.
2018, vol. 25, no. 8, pp.
930-936.
https://doi.org/10.1007/s12613-018-1642-3
Abstract:
In this work, a series of specimens was prepared by the casting method. Sharp cube-textured substrates were processed by heavy cold rolling and recrystallization annealing (i.e., the rolling-assisted biaxially textured substrates (RABiTS) method). Both the rolling and the recrystallization texture in the alloy tapes were investigated by X-ray diffraction and electron back-scatter diffraction, respectively. The results showed that a strong copper-type deformation texture was obtained in the heavy cold-rolled substrate. In addition, the recrystallization annealing process was found to be very important for the texture transition in the Cu–Ni alloy substrates. The cube texture content in the Cu60Ni40 alloy substrates reached 99.7% (≤10°) after optimization of the cold-rolling procedure and the recrystallizing heat-treatment process, whereas the content of low-angle grain boundaries (from 2° to 10° misorientation) in the substrate reached 95.1%.
In this work, a series of specimens was prepared by the casting method. Sharp cube-textured substrates were processed by heavy cold rolling and recrystallization annealing (i.e., the rolling-assisted biaxially textured substrates (RABiTS) method). Both the rolling and the recrystallization texture in the alloy tapes were investigated by X-ray diffraction and electron back-scatter diffraction, respectively. The results showed that a strong copper-type deformation texture was obtained in the heavy cold-rolled substrate. In addition, the recrystallization annealing process was found to be very important for the texture transition in the Cu–Ni alloy substrates. The cube texture content in the Cu60Ni40 alloy substrates reached 99.7% (≤10°) after optimization of the cold-rolling procedure and the recrystallizing heat-treatment process, whereas the content of low-angle grain boundaries (from 2° to 10° misorientation) in the substrate reached 95.1%.
2018, vol. 25, no. 8, pp.
937-949.
https://doi.org/10.1007/s12613-018-1643-2
Abstract:
The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used. In this work, multiscale metallurgical observations using scanning electron microscopy, electron-backscatter diffraction microscopy, and transmission electron microscopy were conducted to quantitatively characterize the microstructure of the machined subsurface. Next, to elucidate the factors that affect the formation of the refinement microstructure, the distributions of the deformation parameters (strain, strain rate, and temperature) in the machined subsurface were analyzed. A dislocation–twin interaction dynamic recrystallization mechanism for grain refinement during machining of Inconel 718 is proposed. Furthermore, microhardness evolution induced by grain refinement in the machined surface is evaluated. The results suggest that the gradient microstructure and the work hardening can be optimized by controlling the cutting parameters during turning of Inconel 718.
The microstructural changes in the machined surface layer of Ni-based super alloys essentially determine the final performance of the structural components of aerospace engines in which these alloys are used. In this work, multiscale metallurgical observations using scanning electron microscopy, electron-backscatter diffraction microscopy, and transmission electron microscopy were conducted to quantitatively characterize the microstructure of the machined subsurface. Next, to elucidate the factors that affect the formation of the refinement microstructure, the distributions of the deformation parameters (strain, strain rate, and temperature) in the machined subsurface were analyzed. A dislocation–twin interaction dynamic recrystallization mechanism for grain refinement during machining of Inconel 718 is proposed. Furthermore, microhardness evolution induced by grain refinement in the machined surface is evaluated. The results suggest that the gradient microstructure and the work hardening can be optimized by controlling the cutting parameters during turning of Inconel 718.
2018, vol. 25, no. 8, pp.
950-956.
https://doi.org/10.1007/s12613-018-1644-1
Abstract:
Through electrospinning, La2CoMnO6 nanofibers were prepared from a polyvinylpyrrolidone/lanthanum nitrate–cobalt acetate–manganese acetate (PVP/LCM) precursor and were used as electrode materials. The morphologies and structures of the samples were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) specific surface area analysis. The results show that the prepared La2CoMnO6 nanofibers are stable, one-dimensional structures formed from interconnected La2CoMnO6 nanoparticles with a diamond-like crystal structure. The specific surface area of the fibers is 79.407 m2·g-1. Electrochemical performance tests with a three-electrode system reveal the specific capacitance of the La2CoMnO6 nanofibers as 109.7 F·g-1 at a current density of 0.5 A·g-1. After 1000 charge-discharge cycles at a current density of 1 A·g-1, the specific capacitance maintains 90.9% of its initial value, demonstrating a promising performance of the constraint capacitance and good cyclic stability.
Through electrospinning, La2CoMnO6 nanofibers were prepared from a polyvinylpyrrolidone/lanthanum nitrate–cobalt acetate–manganese acetate (PVP/LCM) precursor and were used as electrode materials. The morphologies and structures of the samples were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) specific surface area analysis. The results show that the prepared La2CoMnO6 nanofibers are stable, one-dimensional structures formed from interconnected La2CoMnO6 nanoparticles with a diamond-like crystal structure. The specific surface area of the fibers is 79.407 m2·g-1. Electrochemical performance tests with a three-electrode system reveal the specific capacitance of the La2CoMnO6 nanofibers as 109.7 F·g-1 at a current density of 0.5 A·g-1. After 1000 charge-discharge cycles at a current density of 1 A·g-1, the specific capacitance maintains 90.9% of its initial value, demonstrating a promising performance of the constraint capacitance and good cyclic stability.
2018, vol. 25, no. 8, pp.
957-966.
https://doi.org/10.1007/s12613-018-1645-0
Abstract:
The effect of particle size distribution on the microstructure, texture, and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties, microstructure, and texture of the alloy. The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture. After the pre-aging treatment and natural aging treatment (T4P treatment), in contrast to the sheet with a uniform particle size distribution, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio (r) and strain hardening exponent (n). After solution treatment, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution. Additionally, they possess almost identical weak recrystallization textures, and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.
The effect of particle size distribution on the microstructure, texture, and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties, microstructure, and texture of the alloy. The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture. After the pre-aging treatment and natural aging treatment (T4P treatment), in contrast to the sheet with a uniform particle size distribution, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio (r) and strain hardening exponent (n). After solution treatment, the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution. Additionally, they possess almost identical weak recrystallization textures, and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.
2018, vol. 25, no. 8, pp.
967-973.
https://doi.org/10.1007/s12613-018-1646-z
Abstract:
This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754. Samples of various joints were prepared by applying different rotational and welding speeds, and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis. The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5wt% NaCl aqueous solution, and sound welds were obtained in the presence of the Zn interlayer foil. The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7xxx series, and as such, it showed the best resistance to corrosion.
This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754. Samples of various joints were prepared by applying different rotational and welding speeds, and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis. The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5wt% NaCl aqueous solution, and sound welds were obtained in the presence of the Zn interlayer foil. The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7xxx series, and as such, it showed the best resistance to corrosion.
2018, vol. 25, no. 8, pp.
974-980.
https://doi.org/10.1007/s12613-018-1647-y
Abstract:
The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state. Results show that the shape formation of closed-cell aluminum foam in the solid–liquid–gas coexisting state was realized through cell wall deformation and cell movement caused by primary α-Al grains that slid, rotated, deformed, and ripened within cell walls. During formation, characteristic parameters of closed-cell aluminum foam were almost unchanged. Under proper forming conditions, shaped products of closed-cell aluminum foam could be fabricated through mold pressing.
The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state. Results show that the shape formation of closed-cell aluminum foam in the solid–liquid–gas coexisting state was realized through cell wall deformation and cell movement caused by primary α-Al grains that slid, rotated, deformed, and ripened within cell walls. During formation, characteristic parameters of closed-cell aluminum foam were almost unchanged. Under proper forming conditions, shaped products of closed-cell aluminum foam could be fabricated through mold pressing.
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