27 results on '"Wu, K."'
Search Results
2. The effect of thermal exposure on the interface and mechanical properties of Al18B4O33w/AZ91 magnesium matrix composite
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Zheng, M.Y., Wu, K., Liang, M., Kamado, S., and Kojima, Y.
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MECHANICAL properties of metals , *MAGNESIUM , *BORATES , *ALUMINUM - Abstract
The effect of high temperature exposure on the interface and tensile properties of Al18B4O33w/AZ91 magnesium matrix composite fabricated by squeeze casting was studied. The interfaces of the composites were examined using transmission electron microscopy, and the mechanical properties were evaluated by tensile tests. The interfacial region was composed of MgO which was formed by the reaction between the Al18B4O33 whisker and the Mg matrix. An thin and uniform interfacial reaction layer with a thickness of 10–20 nm formed during squeeze casting could act as a barrier to prevent the further reaction between Al18B4O33 whisker and Mg alloys. The interfacial reaction rate was very low during thermal exposure below the liquidus temperature of AZ91 matrix alloy. Only after exposure above the liquidus temperature of the AZ91 matrix alloy for a long period, the thickness of the interfacial layer increased obviously. However, the interfacial reaction rate was much slower than that in the Al18B4O33w/Al–Mg composites. The interfacial reaction kinetics was controlled by the seepage of Mg and release of Al and B along the narrow diffusion channels between the fine MgO particle. The composite did not show a degradation in the tensile properties after exposure below the solidus temperature of AZ91 for long periods, suggesting that the Al18B4O33w/AZ91 magnesium matrix composite could be subjected to long-term service at elevated temperature. [Copyright &y& Elsevier]
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- 2004
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3. Influence of rolling temperature on the microstructure and mechanical properties of Mg–Gd–Y–Zn–Zr alloy sheets
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Xu, C., Zheng, M.Y., Wu, K., Wang, E.D., Fan, G.H., Xu, S.W., Kamado, S., Liu, X.D., Wang, G.J., and Lv, X.Y.
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ZIRCONIUM alloys , *ROLLING (Metalwork) , *METAL microstructure , *MECHANICAL properties of metals , *STRAINS & stresses (Mechanics) , *CRYSTAL grain boundaries , *PHASE distortion (Electronics) - Abstract
Abstract: The extruded Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy were subjected to large-strain hot rolling with different final rolling temperatures. The microstructural evolution and mechanical properties of the sheets were investigated. The microstructure became homogeneous after hot rolling process and long period stacking ordered (LPSO) phase distributed at grain boundaries along rolling direction. The sheet rolled at 300°C was composed of deformed grains, substructures and excessive dislocations. With increasing final rolling temperatures from 300°C to 400°C, the volume fraction of recrystallized grains with relatively random orientations increased significantly. The strength of the rolled sheets was improved while the ductility was deteriorated with decreasing final rolling temperatures. The tensile yield strength and ultimate tensile strength of the sheet rolled at 300°C reached 320MPa and 416MPa, respectively with the elongation to failure of 5.3%. The mechanical anisotropy of the rolling sheet became unity when rolled at higher temperature of 400°C due to the formation of weaker basal texture. [Copyright &y& Elsevier]
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- 2013
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4. Effect of cooling rate on the microstructure evolution and mechanical properties of homogenized Mg–Gd–Y–Zn–Zr alloy
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Xu, C., Zheng, M.Y., Wu, K., Wang, E.D., Fan, G.H., Xu, S.W., Kamado, S., Liu, X.D., Wang, G.J., and Lv, X.Y.
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MANGANESE alloys , *COOLING , *METAL microstructure , *MECHANICAL properties of metals , *METAL quenching , *CRYSTAL grain boundaries , *PARTICLE size distribution , *STRENGTH of materials - Abstract
Abstract: Different cooling processes, such as quenching in warm water and cooling in furnace, were introduced to homogenize Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy. Microstructure evolution and mechanical properties of the homogenized alloy were investigated. The as-quenched sample was comprised of α-Mg matrix, Mg5RE phase and 18R LPSO phase distributed at the grain boundaries and a few of RE-rich particles distributed randomly. During the process of cooling in furnace, Mg5RE and 18R LPSO phases were transformed into block-shaped 14H LPSO phase and lamellar-shaped 14H LPSO phase, respectively, due to the diffusion of solute atoms into the α-Mg matrix. Furthermore, the lamellar-shaped 14H LPSO phase grew and ran through the whole grains. The as-quenched sample exhibits tensile yield strength of 130MPa, ultimate tensile strength of 206MPa and elongation to failure of 5.5%, while the sample cooled in the furnace exhibits higher tensile yield strength but lower ultimate tensile strength and ductility due to the coarse grains and formation of block-shaped 14H LPSO phase. [Copyright &y& Elsevier]
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- 2013
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5. Effect of final rolling reduction on the microstructure and mechanical properties of Mg–Gd–Y–Zn–Zr alloy sheets
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Xu, C., Zheng, M.Y., Wu, K., Wang, E.D., Fan, G.H., Xu, S.W., Kamado, S., Liu, X.D., Wang, G.J., Lv, X.Y., Li, M.J., and Liu, Y.T.
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MANGANESE alloys , *ROLLING (Metalwork) , *METAL microstructure , *MECHANICAL properties of metals , *METALS , *CRYSTAL texture , *RECRYSTALLIZATION (Metallurgy) - Abstract
Abstract: The Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt.%) alloy was hot rolled with different final rolling reductions at 400°C. The microstructure evolution and texture of the sheets were analyzed, and their effect on the mechanical properties was discussed. All of the rolled sheets consist of fine dynamically recrystallized grains with almost random orientation, large deformed grains with strong basal texture. In addition, bent lamellar-shaped long period stacking ordered (LPSO) phases due to kink deformation were observed in the deformed grains. The volume fraction of the dynamic recrystallization increased with increasing final rolling reduction and the basal texture weakened gradually. The strength of the alloy sheets changed a little with increasing final rolling reduction, while the yield anisotropy and the ductility were significantly improved. The sheet final-rolled with thickness reduction of 60% exhibits tensile yield strength of 306MPa, ultimate tensile strength of 393MPa and elongation to failure of 14.6% at ambient temperature, and tensile yield strength of 264MPa, ultimate tensile strength of 345MPa and elongation to failure of 19.4% at 250°C. [Copyright &y& Elsevier]
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- 2013
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6. Microstructure and mechanical properties of the accumulative roll bonded (ARBed) pure magnesium sheet
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Chang, H., Zheng, M.Y., Wu, K., Gan, W.M., Tong, L.B., and Brokmeier, H.-G.
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METAL microstructure , *MECHANICAL properties of metals , *SHEET metal , *MAGNESIUM , *METAL bonding , *HEAT treatment of metals , *CRYSTAL texture , *METALS - Abstract
Abstract: The pure Mg sheets were processed by ARB at 400°C and 300°C up to 8 cycles and 4 cycles, respectively. The microstructure was refined during the first cycle and only homogenized during the following ARB process due to the high deformation temperature, intermediate reheating and air-cooling. The ARB process did not show an obvious effect on the tensile properties of the as-ARBed pure Mg sheet due to the stable grain size and dominant basal plane texture during ARB. Further deformation should be introduced to improve the bonding quality of the as-ARBed sheet. [ABSTRACT FROM AUTHOR]
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- 2010
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7. Microstructure and mechanical properties of WE43 magnesium alloy fabricated by direct-chill casting.
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Jiang, H.S., Zheng, M.Y., Qiao, X.G., Wu, K., Peng, Q.Y., Yang, S.H., Yuan, Y.H., and Luo, J.H.
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MAGNESIUM alloys , *INGOTS , *METAL microstructure , *MECHANICAL properties of metals , *METAL castings , *GRAIN size - Abstract
High quality WE43 magnesium alloy ingots with diameter of 500 mm are successfully fabricated by direct-chill (DC) casting. The alloying elements distributed almost homogeneously across the large ingot. With the average grain size decreasing from the center to the edge of the ingot, the mechanical properties are improved gradually. After solution treatment at 525 °C for 8 h, the Mg 14 Nd 2 Y phases distributing along the grain boundaries are well dissolved into matrix. The direct-chill (DC) casting ingot exhibits remarkable age-hardening response from 85 Hv to 117 Hv after T6 treatment at 250 °C. The T6 peak-aged sample exhibits ultimate tensile strength of 274 MPa, yield strength of 215 MPa and elongation to failure of 3.4%, which are higher than those of sand-cast and permanent mold cast WE43 alloys. The large amount of nano prismatic β ′ and β 1 phases precipitated during T6 treatment contribute to improved strength of the WE43 alloy. [ABSTRACT FROM AUTHOR]
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- 2017
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8. Effect of Ca/Al ratio on microstructure and mechanical properties of Mg-Al-Ca-Mn alloys.
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Li, Z.T., Zhang, X.D., Zheng, M.Y., Qiao, X.G., Wu, K., Xu, C., and Kamado, S.
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MAGNESIUM alloys , *CALCIUM , *MECHANICAL properties of metals , *METAL microstructure , *METAL extrusion , *STRENGTH of materials - Abstract
The effect of Ca/Al ratio on microstructure and mechanical properties of the as-cast and as-extruded Mg-Al-Ca-Mn alloys were investigated. The as-cast Mg-Al-Ca-Mn alloys with Ca/Al mass ratios less than 0.50 contain divorced and lamellar eutectic (Mg,Al) 2 Ca. When Ca/Al ratio is greater than 0.90, fine lamellar Mg 2 Ca phase is formed in the as-cast Mg-Al-Ca-Mn alloys. After extrusion, the second phases are broken and dispersed along the extrusion direction. The area fraction of DRXed regions decrease with increasing Ca/Al ratio, the microstructure changes from an almost fully recrystallized structure to a bimodal structure consisting of fine dynamically recrystallized (DRXed) grains and coarse deformed regions. With increasing Ca/Al ratio, the DRXed grains and dispersed second phases are refined. The as-extruded alloys exhibit a strong basal fiber texture, the intensity of which is increased with increasing Ca/Al ratio. With increasing Ca/Al ratio, the {0002}<11-20> texture component in the DRXed regions is suppressed, and shifted to a {0002}<10-10> texture component. The strength of the as-extruded Mg-Al-Ca-Mn alloys increases significantly with increasing Ca/Al ratio. The as-extruded Mg-2.7Al-3.5Ca-0.4Mn (wt%) alloy exhibits a tensile proof strength of 438 MPa and an ultimate tensile strength of 457 MPa. The extraordinary high strengths are attributed to the ultrafine DRXed grains pinned by fragmented secondary phases, strong basal texture and dense nano-scale precipitates. The present research indicates that the Mg-Al-Ca-Mn alloys have a great potential as next generation low-cost ultrahigh-strength wrought Mg alloys. [ABSTRACT FROM AUTHOR]
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- 2017
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9. Twinning/detwinning-mediated grain growth and mechanical properties of free-standing nanotwinned Ni foils: Grain size and strain rate effects.
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Li, J., Zhang, J.Y., Jiang, L., Zhang, P., Wu, K., Liu, G., and Sun, J.
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TWINNING (Crystallography) , *METAL crystal growth , *MECHANICAL properties of metals , *NICKEL , *METAL foils , *GRAIN size , *STRAIN rate - Abstract
Both twinning and its reversible process, i.e., detwinning, play important roles in crystalline plasticity, especially for nanostructured metals and alloys. Contrary to the popular belief that the nanotwinned (NT) microstructure is quite stable, in this work, we reported the twinning/detwinning-mediated grain growth (GG) and dislocation nucleation-controlled strength softening in the high stacking fault energy (SFE) NT-Ni foils with different grain sizes but nearly identical twin lamellar thickness during tension at room temperature. We further proposed two possible dislocation–boundary interaction mechanisms that cause GG via twinning/detwinning processes, and elucidated strain rate effect on the double-inverse grain size dependence of twinning/detwinning in nanostructured Ni samples. Our findings provide in-depth insights into the manipulation of internal features of metals and alloys with high SFE to achieve optimum robust performance for practical applications and fundamental understanding of the twinning/detwinning behavior of NT-materials to predict their stability and evolution of microstructures. [ABSTRACT FROM AUTHOR]
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- 2015
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10. The microstructure, texture and mechanical properties of extruded Mg–5.3Zn–0.2Ca–0.5Ce (wt%) alloy.
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Du, Y.Z., Qiao, X.G., Zheng, M.Y., Wu, K., and Xu, S.W.
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MAGNESIUM alloys , *METAL microstructure , *CRYSTAL texture , *MECHANICAL properties of metals , *METAL extrusion , *CRYSTAL grain boundaries - Abstract
Mg–5.3 wt%Zn alloy microalloyed with 0.2 wt%Ca and 0.5 wt%Ce was extruded, and the microstructure, texture and mechanical properties of the as-extruded alloy were investigated. The undissolved coarse T 1 ′during homogenization treatment stimulated nucleation of dynamic recrystallization (DRX) grains during extrusion. The double microalloying with Ca and Ce promoted the dynamic precipitation, resulting in high density precipitates after hot extrusion. Fine Ca 2 Mg 6 Zn 3 particles precipitated dynamically at the grain boundaries (GBs) could effectively hinder the grain growth during hot extrusion. A weaker texture in DRXed grains was attributed to the coarse-particle stimulated nucleation (PSN) and pinning of the grain boundaries by fine precipitates. The fine DRXed grains, high density of dislocation in the unDRXed region, and fine dense precipitates gave rise to the improved strength of the as-extruded Mg–Zn–Ca–Ce alloy. [ABSTRACT FROM AUTHOR]
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- 2015
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11. Microstructure and strengthening mechanism of carbon nanotubes reinforced magnesium matrix composite.
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Li, C.D., Wang, X.J., Liu, W.Q., Wu, K., Shi, H.L., Ding, C., Hu, X.S., and Zheng, M.Y.
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METAL microstructure , *STRENGTH of materials , *CARBON nanotubes , *MAGNESIUM compounds , *METALLIC composites , *MECHANICAL properties of metals , *METAL extrusion - Abstract
Abstract: Carbon nanotube (CNTs) reinforced Mg matrix composites were successfully fabricated by a novel approach. After hot extrusion, the influence of CNTs on microstructure and mechanical properties of Mg–6Zn matrix was investigated. The results showed that most CNTs distributed uniformly and individually in the composites, and good interfacial bonding was achieved. CNTs significantly refined the grains of Mg–6Zn matrix, and the CNTs evidently improved the ultimate tensile strength (UTS), yield strength (YS) and Young's modulus. Grain refinement, load transfer mechanism and Orowan strengthening mechanism play important roles on the increase of the yield strength. [Copyright &y& Elsevier]
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- 2014
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12. Microstructure and mechanical properties of Mg–Zn–Ca–Ce alloy processed by semi-continuous casting.
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Du, Y.Z., Zheng, M.Y., Qiao, X.G., Wu, K., Liu, X.D., Wang, G.J., and Lv, X.Y.
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MAGNESIUM alloys , *MICROSTRUCTURE , *MECHANICAL properties of metals , *METAL castings , *PHASE transitions , *STRENGTH of materials - Abstract
Abstract: The microstructures and mechanical properties of Mg–5.3Zn–0.2Ca–0.5Ce (wt%) alloy fabricated by semi-continuous casting were investigated. The as-cast alloy consists of α-Mg, Ca2Mg6Zn3 and T′1 phase with orthorhombic structure (a=0.57nm, b=0.75nm and c=1.00nm). T′1 phase mainly distributes at the triple conjunctions while the Ca2Mg6Zn3 at the grain boundaries. The as-cast alloy exhibits high strength retention due to the stable Ca2Mg6Zn3 and T′1 phase at the grain boundaries. [Copyright &y& Elsevier]
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- 2013
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13. Microstructures and mechanical properties of as-cast and as-extruded Mg-4.50Zn-1.13Ca (wt%) alloys.
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Du, Y.Z., Zheng, M.Y., Xu, C., Qiao, X.G., Wu, K., Liu, X.D., Wang, G.J., and Lv, X.Y.
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MAGNESIUM alloys , *METAL microstructure , *MECHANICAL properties of metals , *MICROFABRICATION , *CRYSTAL grain boundaries , *CRYSTAL texture , *METALS , *METAL castings - Abstract
Abstract: A large Mg-4.50Zn-1.13Ca (wt%) alloy ingot 350mm in diameter and 1730mm long was successfully fabricated by semi-continuous casting. The microstructures and mechanical properties of the as-cast and as-extruded alloys were investigated. The as-cast alloy exhibits uniform chemical composition and microstructure from the centre to the surface of the ingot and mainly consists of α-Mg and Ca2Mg6Zn3. The coarse grains and network-like second phases that are distributed at the grain boundaries result in poor mechanical properties for the as-cast alloy. The mechanical properties of the as-extruded alloys are significantly enhanced. The high yield strengths of the as-extruded alloys mainly result from the fine DRXed grain and the stronger basal texture. [Copyright &y& Elsevier]
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- 2013
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14. Effect of ageing treatment on the microstructure, texture and mechanical properties of extruded Mg–8.2Gd–3.8Y–1Zn–0.4Zr (wt%) alloy
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Chi, Y.Q., Zheng, M.Y., Xu, C., Du, Y.Z., Qiao, X.G., Wu, K., Liu, X.D., Wang, G.J., and Lv, X.Y.
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MAGNESIUM compounds , *MECHANICAL properties of metals , *METAL microstructure , *EFFECT of temperature on metals , *CRYSTAL texture , *METALS , *RECRYSTALLIZATION (Metallurgy) , *EXTRUSION process - Abstract
Abstract: Extruded Mg–8.2Gd–3.8Y–1Zn–0.4Zr (wt%) alloy was subjected to ageing treatment at 200°C. The microstructures, textures and mechanical properties of the as-extruded and peak-aged alloys were investigated. Recrystallization occurred during ageing treatment. A large number of β′ phases were observed in the peak-aged alloy, accompanied with the decrease of the volume fraction of LPSO phases. A basal fiber texture and an unusual texture component with basal planes perpendicular to the extrusion direction were found in the as-extruded alloy, and the basal fiber texture was strengthened after ageing treatment. The peak-aged alloy exhibited a tensile yield strength (TYS), an ultimate tensile strength (UTS) and an elongation to failure of 395MPa, 470MPa and 8%, respectively, at ambient temperature, and 271MPa, 311MPa and 19%, respectively, at 300°C. The superior strength of the peak-aged alloy was mainly attributed to the precipitation of fine β′ phases, the remaining LPSO phases and the texture modification. [Copyright &y& Elsevier]
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- 2013
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15. Dynamic recrystallization behavior during hot deformation and mechanical properties of 0.2μm SiCp reinforced Mg matrix composite
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Deng, K.K., Wang, X.J., Zheng, M.Y., and Wu, K.
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MAGNESIUM alloys , *RECRYSTALLIZATION (Metallurgy) , *DEFORMATIONS (Mechanics) , *MECHANICAL properties of metals , *METALLIC composites , *FLUX pinning - Abstract
Abstract: In this paper, 0.2μm SiCp/AZ91 composite was fabricated by stir casting technology. The influence of fine (<1μm) particles on the dynamic recrystallization (DRX) behavior of AZ91 matrix was investigated by researching the microstructure evolution of 0.2μm 1vol% SiCp/AZ91 composite during the hot extrusion process. Results showed that the DRXed ratio of AZ91 matrix increased as well as the average size of DRXed grains reduced due to the addition of fine particles. The SiCp could not only pin dislocation, but also was helpful to generate dislocations owing to the deformation mismatch between matrix and particles, thus causing the increase of dislocation density around SiCp, which was benefit to stimulate DRX nucleation. Meanwhile, the growth of DRXed grains was suppressed in the following deformation process due to the pinning effect of fine particles on grain boundaries. Thus, the fine particles had significant effect on stimulating DRXed nucleation and refining grain size. The yield strength and ultimate tensile strength of the as-deformed 0.2μm 1vol% SiCp/AZ91 composite are 275 and 335MPa, respectively, which are mainly attributed to the grain refinement, basal plane texture and uniform particle distribution induced by hot deformation. [Copyright &y& Elsevier]
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- 2013
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16. Microstructure and mechanical properties of Mg–Gd–Y–Zn–Zr alloy sheets processed by combined processes of extrusion, hot rolling and ageing
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Xu, C., Zheng, M.Y., Xu, S.W., Wu, K., Wang, E.D., Fan, G.H., Kamado, S., Liu, X.D., Wang, G.J., and Lv, X.Y.
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ZIRCONIUM alloys , *METAL microstructure , *MECHANICAL properties of metals , *ROLLING (Metalwork) , *METAL extrusion , *STRAINS & stresses (Mechanics) , *CRYSTAL grain boundaries , *STRENGTH of materials - Abstract
Abstract: The microstructure and mechanical properties of Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy sheets produced by combined processes of extrusion, large-strain hot rolling and ageing treatment were investigated. The sheet rolled at 300°C was mainly composed of deformed grains while that rolled at 400°C was fully recrystallized, and the LPSO phase distributed at the grain boundaries in both sheets. The sheet rolled at 300°C and then peak-aged at 200°C exhibits 0.2% proof stress (PS) of 454MPa, ultimate tensile strength (UTS) of 469MPa and elongation to failure of 1.3% at ambient temperature, and 0.2% PS of 413MPa, UTS of 457MPa and elongation to failure of 6.8% at 200°C, respectively. While the sheet rolled at 400°C and peak aged at 200°C had lower 0.2% PS and superior ductility. The improvement of strength is ascribed to the fine β′ phase precipitated within the grains, the LPSO phase and dispersed cuboid Mg–Gd–Y containing phase located at the grain boundaries. [Copyright &y& Elsevier]
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- 2013
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17. Microstructure evolutions of SiCp/AZ91 Mg matrix composites during hot compression
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Wang, X.J., Hu, X.S., Wang, Y.Q., Nie, K.B., Wu, K., and Zheng, M.Y.
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SILICON carbide , *MECHANICAL properties of metals , *METAL microstructure , *METAL castings , *MICROFABRICATION , *STRAINS & stresses (Mechanics) , *PARTICLE size distribution , *CRYSTAL grain boundaries - Abstract
Abstract: 10vol% 10μm SiCp/AZ91 composite fabricated by stir casting was compressed with four temperatures and four strain rates. Compression improved the SiC particle distribution of the composite. Particles segregation was easy to be reduced at higher compressive temperatures. Dynamic recrystallization (DRX) took place in the matrix during hot compression. DRX areas were mainly located near particle aggregations at grain boundaries. Temperatures and strain rates significantly affected the DRX behavior of the matrix, which causes the different microstructures of the composites compressed at different parameters. In addition, temperatures and strain rates also significantly affected the dislocations and twins of the matrix. The secondary twins were observed at higher strain rates. The twins recovered at the higher temperatures and lower strain rates. As temperatures increased, the density and morphology of the dislocations evidently changed. [Copyright &y& Elsevier]
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- 2013
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18. Improved mechanical property and internal friction of pure Mg processed by ECAP
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Fan, G.D., Zheng, M.Y., Hu, X.S., Xu, C., Wu, K., and Golovin, I.S.
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MECHANICAL properties of metals , *FRICTION , *DYNAMIC mechanical analysis , *EXTRUSION process , *HIGH temperatures , *ACTIVATION energy , *POINT defects , *RELAXATION phenomena - Abstract
Abstract: Equal channel angular pressing was performed on the extruded pure Mg. The elongation to failure of the ECAPed pure Mg is enhanced to 27% without sacrificing the strength, which is mainly resulted from both the effective refinement of grain size and the weakening of the basal plane texture. The internal friction mechanisms of magnesium at room and elevated temperature were studied by dynamic mechanical analyzer (DMA). The strain independent internal friction is increased after ECAP processing, while the strain dependent part is obviously decreased. Three internal friction peaks were observed in the temperature dependent internal friction curves. The activation energy is 105kJ/mol for P1 peak, which may be related to the basal dislocation glide controlled by climb of jogs and diffusion of vacancies along dislocations. The activation energy of P2 peak is in the range from 95 to 181kJ/mol, and this obviously broadened peak is associated with grain boundary relaxation. The P3 peak is related to recrystallization. [Copyright &y& Elsevier]
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- 2012
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19. Microstructure and mechanical properties of the Mg–Gd–Y–Zn–Zr alloy fabricated by semi-continuous casting
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Xu, C., Zheng, M.Y., Chi, Y.Q., Chen, X.J., Wu, K., Wang, E.D., Fan, G.H., Yang, P., Wang, G.J., Lv, X.Y., Xu, S.W., and Kamado, S.
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MAGNESIUM alloys , *MECHANICAL properties of metals , *MICROSTRUCTURE , *METAL castings , *CHEMICAL systems , *MICROFABRICATION , *INGOTS , *DUCTILITY , *METALS - Abstract
Abstract: Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy ingot with diameter of 280mm and length of 2940mm was successfully fabricated by semi-continuous casting. The microstructure and mechanical properties of the large ingot at different locations were investigated. The concentration of the RE and Zn elements distributed almost homogeneously through the whole alloy ingot. The average grain size decreased from the center to the surface of the alloy ingot, while the strength and ductility were improved gradually. The main eutectic compounds located at the grain boundaries were (Mg,Zn)3(Gd,Y) phase, adjacent to these eutectic compounds the 14H-type long period stacking ordered (LPSO) phase formed. Furthermore, some block-shaped Mg24(Gd,Y)5 phase and isolated Zr cores can be recognized in the interior of the grains. [Copyright &y& Elsevier]
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- 2012
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20. Microstructure and mechanical properties of the Mg/Al multilayer fabricated by accumulative roll bonding (ARB) at ambient temperature
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Chang, H., Zheng, M.Y., Xu, C., Fan, G.D., Brokmeier, H.G., and Wu, K.
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METAL microstructure , *MECHANICAL properties of metals , *MICROFABRICATION , *ROLLING (Metalwork) , *TEMPERATURE effect , *MAGNESIUM compounds , *METALLIC composites , *LAMINATED materials - Abstract
sAbstract: The Mg/Al laminated composites were fabricated by the accumulative roll bonding (ARB) at ambient temperature using the pure magnesium and commercial pure Al sheets. Mg grains were refined after the primary sandwich preparation and then homogenized during the following ARB process while the grain size of Al layer decreased with increasing of the accumulated strains. Both the yield strength and ultimate strength along rolling direction and transverse direction increased gradually while the elongation to failure along both directions decreased with increasing of the ARB cycles. Formation of the Mg17Al12 phase indicated that the ARB process at ambient temperature could lead to a metallurgic bonding of the Mg/Al interface. [Copyright &y& Elsevier]
- Published
- 2012
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21. Effect of particle size on microstructure and mechanical properties of SiCp/AZ91 magnesium matrix composite
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Deng, K.K., Wang, X.J., Wu, Y.W., Hu, X.S., Wu, K., and Gan, W.M.
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PARTICLE size distribution , *METAL microstructure , *MECHANICAL properties of metals , *SILICON carbide , *MAGNESIUM , *METALLIC composites , *METAL extrusion - Abstract
Abstract: In this paper, three kinds of magnesium matrix composites reinforced by SiCp with the sizes of 0.2, 5 and 10μm, respectively, were fabricated by stir casting technology. Then the as-cast ingots were deformed by the combination of forging and extrusion process. Typical microstructures were obtained in the composites reinforced by different particle sizes. For the composites with lower volume fraction of particles (2%), submicron SiCp had significant influence on grain refinement and strengthening effect, which resulted in better mechanical properties of submicron SiCp/AZ91 composite. However, mechanical properties reduced owing to the obvious agglomerated submicron SiC particles as the volume fraction increased to 5% and 10%. On the contrary, for micron SiCp/AZ91 composite, the grain size was refined and the strengthening effect was enhanced with the increasing of volume fraction. Although particle size has no influence on the texture type, it has different effects on weakening the intensity of texture. [Copyright &y& Elsevier]
- Published
- 2012
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22. Influences of extrusion parameters on microstructure and mechanical properties of particulate reinforced magnesium matrix composites
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Wang, X.J., Xu, L., Hu, X.S., Nie, K.B., Deng, K.K., Wu, K., and Zheng, M.Y.
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METALLIC composites , *METAL microstructure , *MECHANICAL properties of metals , *MAGNESIUM , *METAL extrusion , *METAL fractures , *METAL castings - Abstract
Abstract: SiCp/AZ91 composites fabricated by stir casting were extruded at different extrusion temperatures and ratios. Extrusion reduced the necklace-type particle distribution and improved particle distribution of the composites. As extrusion temperatures and ratios increased, particle distribution was improved, and the grain sizes of matrix increased. The mechanical properties of the composites were improved with the increase of extrusion temperatures and ratios. The microstructure evolution of matrix was not the main influential factor of the mechanical properties of the composites. The particle evolution, which included particle redistribution and particle cracking induced by extrusion, significantly affected the mechanical properties of the extruded composites. [Copyright &y& Elsevier]
- Published
- 2011
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23. Microstructure and mechanical properties of SiC nanoparticles reinforced magnesium matrix composites fabricated by ultrasonic vibration
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Nie, K.B., Wang, X.J., Hu, X.S., Xu, L., Wu, K., and Zheng, M.Y.
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MICROSTRUCTURE , *SILICON compounds , *NANOPARTICLES , *MECHANICAL properties of metals , *ULTRASONICS , *NANOCOMPOSITE materials , *MICROCLUSTERS - Abstract
Abstract: A particulate reinforced magnesium matrix nanocomposite was fabricated by ultrasonic vibration. Compared with as-cast AZ91 alloy, grain size of matrix in the SiCp/AZ91 nanocomposite decreased and morphology of phase Mg17Al12 varied from coarse plates to lamellar precipitates. Although there were still some SiC microclusters in the nanocomposite, most of the SiC nanoparticles were dispersed well outside the microclusters. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite were simultaneously enhanced compared with that of the AZ91 alloy. The study of interface between the SiC nanoparticles and the matrix in the nanocomposite suggested that SiC nanoparticles bonded well with the matrix without interfacial activity. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
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24. Dynamic microstructural changes during hot extrusion and mechanical properties of a Mg–5.0 Zn–0.9 Y–0.16 Zr (wt.%) alloy
- Author
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Xu, S.W., Zheng, M.Y., Kamado, S., Wu, K., Wang, G.J., and Lv, X.Y.
- Subjects
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MAGNESIUM-yttrium alloys , *MICROSTRUCTURE , *METAL extrusion , *MECHANICAL properties of metals , *ELECTRON backscattering , *ELECTRON diffraction , *QUASICRYSTALS , *RECRYSTALLIZATION (Metallurgy) , *PRECIPITATION (Chemistry) - Abstract
Abstract: In this study, firstly, dynamic microstructural changes of an as-cast Mg–5.0 Zn–0.9 Y–0.16 Zr (wt.%) alloy (designated ZWK510) during hot extrusion at 350°C and a ram speed of 3.33mms−1 was systematically investigated by electron backscattering diffraction (EBSD) analysis. The dynamic recrystallization (DRX) mechanism during hot extrusion was discussed. Then, the effect of microstructure and texture on the mechanical properties of the as-extruded alloy specimens at room temperature was discussed. The as-cast ZWK510 alloy consists of a-Mg and quasicrystalline I-phase. During hot extrusion at 350°C, the main DRX mechanism is the continuous DRX near the original grain boundaries. The I-phase can accelerate the DRX behavior near these areas by obstructing the slip of dislocations. The deformation twins and massive blocky substructures formed in original grains can coordinate the DRX process near the original grain boundaries, however the DRX seldom occurs inside of these area. After further deformation, these deformation twins and massive blocky substructures are elongated along the material flow and become so-called unDRXed area, then a bimodal “necklace structure” composed of fine DRXed grains of about 2.1μm and unrecrystallized coarse area is formed. The extruded ZWK510 alloy shows a DRX ratio of about 58% and a typical basal fiber texture of extrusion direction (ED). In the DRXed area around the crushed eutectic I-phase a large number of fine I-phase precipitates are observed pinning at the newly formed DRXed grain boundaries. The 0.2% proof strength and the ultimate tensile strength of the extruded ZWK510 alloy specimen are 317 and 363MPa, respectively, with an elongation to failure of 12%, which have been attributed to strong basal fiber texture, refined grain size as well as the existence of fine precipitates formed during the hot extrusion. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
25. Effect of Mn addition on microstructure, texture and mechanical properties of Mg–Zn–Ca alloy
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Tong, L.B., Zheng, M.Y., Xu, S.W., Kamado, S., Du, Y.Z., Hu, X.S., Wu, K., Gan, W.M., Brokmeier, H.G., Wang, G.J., and Lv, X.Y.
- Subjects
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MAGNESIUM-calcium-zinc alloys , *MECHANICAL properties of metals , *METAL microstructure , *CRYSTAL texture , *METAL extrusion , *DUCTILITY , *METALS - Abstract
Abstract: The effect of trace Mn addition on the microstructure, texture and mechanical properties of the as-cast and as-extruded Mg–5.25wt.% Zn–0.6wt.% Ca (ZX51) alloys was investigated in this study. Mn addition had a negligible effect on the grain size of the as-cast ZX51 alloy. However, the addition of Mn led to the obvious decrease of grain size in the as-extruded Mg–5.25wt.% Zn–0.6wt.% Ca–0.3wt.% Mn (ZXM510) alloy, because the Mn addition restricted the grain growth during the hot extrusion process. After the addition of Mn, the basal fiber texture with most of {0002} planes parallel to the extrusion direction (ED) was significantly enhanced in the as-extruded ZXM510 alloy. Both tensile yield strength (TYS) and ultimate tensile strength (UTS) were increased in the as-extruded ZXM510 alloy, while the ductility was slightly decreased, which was ascribed to the grain refinement and texture strengthening. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
26. Influence of ECAP routes on microstructure and mechanical properties of Mg–Zn–Ca alloy
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Tong, L.B., Zheng, M.Y., Hu, X.S., Wu, K., Xu, S.W., Kamado, S., and Kojima, Y.
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MAGNESIUM-calcium-zinc alloys , *MICROSTRUCTURE , *MECHANICAL properties of metals , *SHEAR (Mechanics) , *STRAINS & stresses (Mechanics) , *CRYSTAL grain boundaries , *METALS , *CRYSTAL texture , *STRENGTH of materials - Abstract
Abstract: Mg–5.25wt.% Zn–0.6wt.% Ca alloy was subjected to equal channel angular pressing (ECAP) at 250°C using route A, Bc and C, respectively, in order to investigate the effect of shearing strain path on microstructure, texture and mechanical properties. Route Bc was the most effective in grain refinement and generating high angle grain boundaries, while route A was the least effective. Different textures were developed when a different ECAP route was applied. After ECAP using route A, the tensile yield strength (TYS) got much higher than those of the as-extruded alloy, which was primarily resulted from the strengthening due to the grain refinement. Because the Schmid factor for basal slip system was changed only a little, the texture soften effect was not obvious. After ECAP using route C, TYS of the Mg alloy was significantly decreased although the grain size was significantly refined, because the texture softening effect was dominant over the strengthening due to the grain refinement. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
27. Microstructure and mechanical properties of Mg–Zn–Ca alloy processed by equal channel angular pressing
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Tong, L.B., Zheng, M.Y., Chang, H., Hu, X.S., Wu, K., Xu, S.W., Kamado, S., and Kojima, Y.
- Subjects
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METAL microstructure , *MECHANICAL properties of metals , *MAGNESIUM-calcium-zinc alloys , *DISLOCATIONS in metals , *METAL refining , *RECRYSTALLIZATION (Metallurgy) , *STRAIN hardening , *METAL extrusion - Abstract
Abstract: An ultrafine-grained (UFG) Mg–5.12wt.% Zn–0.32wt.% Ca alloy with an average grain size of 0.7μm was produced by subjecting the as-extruded alloy to equal channel angular pressing (ECAP) for 4 passes at 250°C. The fine secondary phase restricted the dynamic recrystallized (DRXed) grain growth during the ECAP processing, resulting in a remarkable grain refinement. A new texture was formed in the ECAPed Mg alloy with the {0002} plane inclined at an angle of 58° relative to the extrusion direction. The yield stress (YS) was decreased in the as-ECAPed alloy with finer grains, indicating that the texture softening effect was dominant over the strengthening from grain refinement. The ductility of the as-ECAPed alloy was increased to 18.2%. The grain refinement caused an obvious decrease in work hardening rate in the as-ECAPed alloy during tensile deformation at room temperature. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
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