Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg a...Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.展开更多
The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%incr...The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%increases the volume fraction and refines average size of fine grains(<3μm,FGs),leading to an optimized bimodal-grained structure consisting of coarse grains(CGs)uniformly embedded in FG regions.The sample with 85%reduction exhibits the highest yield strength of~314 MPa,ultimate tensile strength of~381 MPa and elongation of~11%.The high strength is primarily due to the contribution of grain boundaries(GBs)strengthening by FGs(accounting for~65%of strength),meanwhile the improved ductility originates from the optimized bimodal-grained structure and weakened basal texture that favor a higher ductility.The present findings successfully overcome the trade-off dilemma that the largereduction rolling processing on Mg alloys usually enhances strength at expense of ductility.In addition,the intensified heterogeneous deformation and favorable formation of a bimodal-grained microstructure during large-reduct ion HPR was addressed by tracing micro structure evolution details in grains of intere st via quasi-in-situ electron back scattering diffraction(EBSD).The present study can be instructive for further designing novel Mg alloys by tailoring bimodal-grained structures for superior combination of mechanical properties.展开更多
In this study,we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification(SRS)combined with hard-plate rolling(HPR),whose elongation-to-failure increases from~17%to~23%without sacrificing tensi...In this study,we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification(SRS)combined with hard-plate rolling(HPR),whose elongation-to-failure increases from~17%to~23%without sacrificing tensile strength(~290 MPa)compared with its counterpart processed via conventional solidification(CS)followed by HPR.Notably,both samples feature a similar refined grain structure with an average grain size of~2.1 and~2.5μm,respectively.However,the high cooling rate of~150 K/s introduced by SRS modified both the size and morphology of Ca_(2)Mg_(6)Zn_(3) eutectic phase in comparison to those coarse ones under CS condition.By subsequent HPR,the Ca_(2)Mg_(6)Zn_(3) phase was further refined and dispersed uniformly by severe fragmentation.Specially,the achieved supersaturation containing excessive Ca solute atoms due to high cooling rate was maintained in the SRS-HPR condition.The mechanisms that govern the high ductility of the SRS-HPR sample could be ascribed to following reasons.First,refined Ca_(2)Mg_(6)Zn_(3) eutectic phase could effectively alleviate or avoid the crack initiation.Furthermore,excessive Ca solute atoms inα-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability during tension.The findings proposed a short-processed strategy towards superior performance of Mg-6Zn-0.2Ca alloy for industrial applications.展开更多
基金The Natural Science Foundation of China under Grant Nos.51922048,51871108 and 51625402Partial financial support came from the Fundamental Research Funds for the Central Universities,JLU,Program for JLU Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09)The Science and Technology Development Program of Jilin Province(No.20200201193JC)。
文摘Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific strength.Most of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide applications.However,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of strength.To identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing technologies.Moreover,some outlooks on enhanced ductility of Mg alloys are suggested,e.g.enhancing the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,etc.The current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.
基金supported by the Natural Science Foundation of China(Nos.51922048,51625402,51871108 and 51671093)Partial financial support came from the Changjiang Scholars Program(No.T2017035)。
文摘The effect of large thickness-reduction on microstructure evolution and tensile properties of Mg-9 Al-1 Zn alloy(AZ91)processed by hard-plate rolling(HPR)was investigated.Increasing rolling reduction from55%to 85%increases the volume fraction and refines average size of fine grains(<3μm,FGs),leading to an optimized bimodal-grained structure consisting of coarse grains(CGs)uniformly embedded in FG regions.The sample with 85%reduction exhibits the highest yield strength of~314 MPa,ultimate tensile strength of~381 MPa and elongation of~11%.The high strength is primarily due to the contribution of grain boundaries(GBs)strengthening by FGs(accounting for~65%of strength),meanwhile the improved ductility originates from the optimized bimodal-grained structure and weakened basal texture that favor a higher ductility.The present findings successfully overcome the trade-off dilemma that the largereduction rolling processing on Mg alloys usually enhances strength at expense of ductility.In addition,the intensified heterogeneous deformation and favorable formation of a bimodal-grained microstructure during large-reduct ion HPR was addressed by tracing micro structure evolution details in grains of intere st via quasi-in-situ electron back scattering diffraction(EBSD).The present study can be instructive for further designing novel Mg alloys by tailoring bimodal-grained structures for superior combination of mechanical properties.
基金This work was primarily supported by the Natural Science Foundation of China(Nos.51922048,51871108,51625402 and 52001133)Partial financial support came from the Fundamental Research Funds for the Central Universities,JLU+1 种基金Program for JLU Science and Technology Innovative Research Team(No.JLUSTIRT,2017TD-09)the Changjiang Scholars Program(No.T2017035)。
文摘In this study,we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification(SRS)combined with hard-plate rolling(HPR),whose elongation-to-failure increases from~17%to~23%without sacrificing tensile strength(~290 MPa)compared with its counterpart processed via conventional solidification(CS)followed by HPR.Notably,both samples feature a similar refined grain structure with an average grain size of~2.1 and~2.5μm,respectively.However,the high cooling rate of~150 K/s introduced by SRS modified both the size and morphology of Ca_(2)Mg_(6)Zn_(3) eutectic phase in comparison to those coarse ones under CS condition.By subsequent HPR,the Ca_(2)Mg_(6)Zn_(3) phase was further refined and dispersed uniformly by severe fragmentation.Specially,the achieved supersaturation containing excessive Ca solute atoms due to high cooling rate was maintained in the SRS-HPR condition.The mechanisms that govern the high ductility of the SRS-HPR sample could be ascribed to following reasons.First,refined Ca_(2)Mg_(6)Zn_(3) eutectic phase could effectively alleviate or avoid the crack initiation.Furthermore,excessive Ca solute atoms inα-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability during tension.The findings proposed a short-processed strategy towards superior performance of Mg-6Zn-0.2Ca alloy for industrial applications.
