Mg-Zn-RE alloys typically exhibit non-basal texture,weak dispersion hardening,and low yield strength.In this study,we designed a dilute quaternary Mg-0.6Zn-0.4Nd-0.2Ca(wt.%)alloy.Then,applied pre-strain and heat treat...Mg-Zn-RE alloys typically exhibit non-basal texture,weak dispersion hardening,and low yield strength.In this study,we designed a dilute quaternary Mg-0.6Zn-0.4Nd-0.2Ca(wt.%)alloy.Then,applied pre-strain and heat treatment to investigate the balance of yield strength and ductility via solute atom segregation at twin boundaries and nanophase modifications.The results indicated that Zn and Nd elements tend to co-segregate at the twin boundary,while Ca element segregates alone and presents a discontinuous distribution.Nanoscale precipitates of(Mg,Zn)_(3)Nd and Mg_(2)Ca with the size of 5∼20 nm underwent significant preferential precipitation at the twin boundary.Moreover,compared with Ca atoms,Zn atoms tend to combine with Nd atoms more preferentially towards the stacking faults,thereby forming a high-density monolayer Guinier-Preston(G.P.)zone.The segregation and precipitation of solute atoms at the twin boundary and the stacking faults increased the friction stress of twinning dislocations and lattice dislocations,thus improving the strength.Pinned twin boundaries facilitate the transition from basalslip to pyramidal<c+a>slip due to the small geometrical compatibility factor(m′)value as well as the Schmid factor(SF)incompatibility.As a result,the pre-strained and heat-treated specimen’s yield strength exhibits a 141%increase relative to the initial state specimen,accompanied by a modest improvement in ductility.The mechanism of multi-element segregation and precipitation at twin boundaries,and G.P.zone formation was discussed in detail.展开更多
基金support from the National Natural Science Foundation of China(Grant No 52471119,Grant No 52301133 and Grant No 52271092)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No YESS20210415)+3 种基金the China Postdoctoral Science Foundation(Grant No 2023M730276)the Chongqing Science and Technology Commission(Grant No CSTB2023NSCQ-MSX0901 and Grant No CSTB2024NSCQ-LZX0006)the Chongqing Municipal Education Commission(Grant No KJQN202101525)the Chongqing University of Science and Technology(Grant No ckrc2021022 and Grant No YKJCX2420218).
文摘Mg-Zn-RE alloys typically exhibit non-basal texture,weak dispersion hardening,and low yield strength.In this study,we designed a dilute quaternary Mg-0.6Zn-0.4Nd-0.2Ca(wt.%)alloy.Then,applied pre-strain and heat treatment to investigate the balance of yield strength and ductility via solute atom segregation at twin boundaries and nanophase modifications.The results indicated that Zn and Nd elements tend to co-segregate at the twin boundary,while Ca element segregates alone and presents a discontinuous distribution.Nanoscale precipitates of(Mg,Zn)_(3)Nd and Mg_(2)Ca with the size of 5∼20 nm underwent significant preferential precipitation at the twin boundary.Moreover,compared with Ca atoms,Zn atoms tend to combine with Nd atoms more preferentially towards the stacking faults,thereby forming a high-density monolayer Guinier-Preston(G.P.)zone.The segregation and precipitation of solute atoms at the twin boundary and the stacking faults increased the friction stress of twinning dislocations and lattice dislocations,thus improving the strength.Pinned twin boundaries facilitate the transition from basalslip to pyramidal<c+a>slip due to the small geometrical compatibility factor(m′)value as well as the Schmid factor(SF)incompatibility.As a result,the pre-strained and heat-treated specimen’s yield strength exhibits a 141%increase relative to the initial state specimen,accompanied by a modest improvement in ductility.The mechanism of multi-element segregation and precipitation at twin boundaries,and G.P.zone formation was discussed in detail.
