Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The result...Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The results show that compared with the intrinsic absorption of Mg-3Ni-2MnO2 hydrogen storage material, the accumulated absorption kinetics of the reaction bed behaves so differently. At 150-300℃ during absorption process, the higher the temperature is, the better the intrinsic kinetics behaves. But during the same temperature range, the lower the initial temperature of the reaction bed is, the better the accumulated absorption kinetics is. During the absorption process, the temperature of reaction bed wall is lower than that of center, and the initial temperature has no influence on the highest temperature in the center of the reaction bed . When the reaction is finished, the reaction bed temperature turns to be homogeneous gradually.展开更多
The effect of different extrusion parameters on the microstructure and mechanical properties of Mg-4Sm-3Gd-2Yb-0.5Zr(SGY2)alloy was investigated.It was observed that under different extrusion parameters,unDRXed grains...The effect of different extrusion parameters on the microstructure and mechanical properties of Mg-4Sm-3Gd-2Yb-0.5Zr(SGY2)alloy was investigated.It was observed that under different extrusion parameters,unDRXed grains of SGY2 alloy exhibited a pronounced basal plane texture,specifically<01.10>//ED,while the texture of DRXed grains was relatively dispersed.Under the condition of 420℃ and an extrusion ratio of 9.4(420℃-ER9.4),the basal plane texture intensity of unDRXed grains in SGY2 alloy was the highest.Furthermore,SGY2 alloy at different extrusion parameters exhibited recrystallization mechanisms mainly characterized by continuous dynamic recrystallization(CDRX),with some DRXed grains and deformed grains experiencing discontinuous dynamic recrystallization(DDRX).Additionally,at the 420℃-ER9.4,the second phase particles in the as-extruded SGY2 alloy were smaller in size and exhibited a dispersed distribution.Under this condition,a significant amount of dislocation accumulation,dislocation bypassing,and dislocation tangling phenomena were observed in the SGY2 alloy.The primary deformation mechanism of unDRXed grains in the SGY2 alloy at the 420℃-ER9.4 may involve prismatic plane,pyramidal plane,and pyramidal plane<c+a>slip,thereby activating a significant amount of dislocations.Compared to other extrusion conditions,this condition is more prone to activate non-basal plane slip.The as-extruded SGY2 alloy exhibited superior mechanical properties,with ultimate tensile strength(UTS)and yield strength(YS)of 332 MPa and 278 MPa,respectively.This is mainly attributed to the extremely fine grains,with many DRXed grains having grain sizes smaller than 1μm,and higher density grain boundaries produced under this condition.Additionally,the unDRXed grains contain a high density of dislocations with small Schmid factor(SF),thus effectively inhibiting basal plane slip and strengthening the alloy to some extent.Similarly,the increased presence of second phase particles will also contribute to strengthening the alloy matrix through precipitation hardening.展开更多
Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant de...Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.展开更多
文摘Mg-3Ni-2MnO2 nanocomposite is fabricated by mechanical-milling under hydrogen atmosphere with the pressure of 0.5MPa, and heat and mass transfer of reaction bed was measured through the self-made apparatus. The results show that compared with the intrinsic absorption of Mg-3Ni-2MnO2 hydrogen storage material, the accumulated absorption kinetics of the reaction bed behaves so differently. At 150-300℃ during absorption process, the higher the temperature is, the better the intrinsic kinetics behaves. But during the same temperature range, the lower the initial temperature of the reaction bed is, the better the accumulated absorption kinetics is. During the absorption process, the temperature of reaction bed wall is lower than that of center, and the initial temperature has no influence on the highest temperature in the center of the reaction bed . When the reaction is finished, the reaction bed temperature turns to be homogeneous gradually.
基金financially supported by the National Natural Science Foundation of China(No.52371108,52201119)Frontier Exploration Project of Longmen Laboratory,China(LMQYTSKT014).
文摘The effect of different extrusion parameters on the microstructure and mechanical properties of Mg-4Sm-3Gd-2Yb-0.5Zr(SGY2)alloy was investigated.It was observed that under different extrusion parameters,unDRXed grains of SGY2 alloy exhibited a pronounced basal plane texture,specifically<01.10>//ED,while the texture of DRXed grains was relatively dispersed.Under the condition of 420℃ and an extrusion ratio of 9.4(420℃-ER9.4),the basal plane texture intensity of unDRXed grains in SGY2 alloy was the highest.Furthermore,SGY2 alloy at different extrusion parameters exhibited recrystallization mechanisms mainly characterized by continuous dynamic recrystallization(CDRX),with some DRXed grains and deformed grains experiencing discontinuous dynamic recrystallization(DDRX).Additionally,at the 420℃-ER9.4,the second phase particles in the as-extruded SGY2 alloy were smaller in size and exhibited a dispersed distribution.Under this condition,a significant amount of dislocation accumulation,dislocation bypassing,and dislocation tangling phenomena were observed in the SGY2 alloy.The primary deformation mechanism of unDRXed grains in the SGY2 alloy at the 420℃-ER9.4 may involve prismatic plane,pyramidal plane,and pyramidal plane<c+a>slip,thereby activating a significant amount of dislocations.Compared to other extrusion conditions,this condition is more prone to activate non-basal plane slip.The as-extruded SGY2 alloy exhibited superior mechanical properties,with ultimate tensile strength(UTS)and yield strength(YS)of 332 MPa and 278 MPa,respectively.This is mainly attributed to the extremely fine grains,with many DRXed grains having grain sizes smaller than 1μm,and higher density grain boundaries produced under this condition.Additionally,the unDRXed grains contain a high density of dislocations with small Schmid factor(SF),thus effectively inhibiting basal plane slip and strengthening the alloy to some extent.Similarly,the increased presence of second phase particles will also contribute to strengthening the alloy matrix through precipitation hardening.
基金financially supported by the National Defense Basic Research Program(No.JCKY2023204A005)Project of High Modulus Magnesium Alloy Forgings(JXXT-2023-014hbza)+1 种基金Research Program of Joint Research Center of Advanced Spaceflight Technologies(No.USCAST2023-3)Major Scientific and Technological Innovation Project of Luoyang(No.2201029A).
文摘Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.
