The microstructures and mechanical properties of Mg-x Bi(x=2,5,and 8 wt%)were investigated compared with pure Mg.The ascast Mg-Bi billets consist of dendriticα-Mg grain matrix,divorced eutectic Mg_(3)Bi_(2)phase and ...The microstructures and mechanical properties of Mg-x Bi(x=2,5,and 8 wt%)were investigated compared with pure Mg.The ascast Mg-Bi billets consist of dendriticα-Mg grain matrix,divorced eutectic Mg_(3)Bi_(2)phase and secondary precipitated Mg_(3)Bi_(2)phase.After homogenization,secondary precipitated Mg_(3)Bi_(2)particles were all dissolved into the matrix,while most of the divorced eutectic Mg_(3)Bi_(2)intermetallic compounds retained.All the as-extruded samples exhibit fully dynamic recrystallization(DRX)and the average grain size decreases and the amount of nano-scale Mg_(3)Bi_(2)precipitates increases with increasing Bi content.Additionally,Bi alloying has little influence on the texture of the as-extruded pure Mg,with all the samples showing typical basal texture.As the results of grain refinement and precipitation hardening,the strengths of the as-extruded samples increase under both tensile and compressive tests.Besides,the yield asymmetry significantly decreases with Bi content.Moreover,all the as-extruded samples represent similar ductility under compression,while the tensile elongation first increases and then decreases with more Bi added.The as-extruded Mg-5Bi alloy demonstrates good combination of strength and ductility.However,Mg-8Bi alloy displays lower tensile ductility than that of Mg-5Bi alloy due to the presence of abundant undissolved coarse Mg_(3)Bi_(2)particles,which act as cracking sources during tensile test.Furthermore,the strain hardening rate,strain hardening exponent n,and hardening capacity Hc are greatly reduced by Bi addition,mainly owing to the enhanced synergy effects of grain refinement and numerous Mg_(3)Bi_(2)precipitates.展开更多
基金supported by the National Natural Science Foundation of China(grant number 51701060)the Natural Science Foundation of Hebei Province(grant number E2016202130)+4 种基金Tianjin city(grant number 18JCQNJC03900)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Hebei Province(grant number C20190505)100 Foreign Experts Plan of Hebei Provincethe National Research Council of Science&Technology(NST)grant by the Korea government(MSIP)(grant number CRC–15–06–KIGAM)the Joint Doctoral Training Foundation of HEBUT(grant number 2018HW0008)。
文摘The microstructures and mechanical properties of Mg-x Bi(x=2,5,and 8 wt%)were investigated compared with pure Mg.The ascast Mg-Bi billets consist of dendriticα-Mg grain matrix,divorced eutectic Mg_(3)Bi_(2)phase and secondary precipitated Mg_(3)Bi_(2)phase.After homogenization,secondary precipitated Mg_(3)Bi_(2)particles were all dissolved into the matrix,while most of the divorced eutectic Mg_(3)Bi_(2)intermetallic compounds retained.All the as-extruded samples exhibit fully dynamic recrystallization(DRX)and the average grain size decreases and the amount of nano-scale Mg_(3)Bi_(2)precipitates increases with increasing Bi content.Additionally,Bi alloying has little influence on the texture of the as-extruded pure Mg,with all the samples showing typical basal texture.As the results of grain refinement and precipitation hardening,the strengths of the as-extruded samples increase under both tensile and compressive tests.Besides,the yield asymmetry significantly decreases with Bi content.Moreover,all the as-extruded samples represent similar ductility under compression,while the tensile elongation first increases and then decreases with more Bi added.The as-extruded Mg-5Bi alloy demonstrates good combination of strength and ductility.However,Mg-8Bi alloy displays lower tensile ductility than that of Mg-5Bi alloy due to the presence of abundant undissolved coarse Mg_(3)Bi_(2)particles,which act as cracking sources during tensile test.Furthermore,the strain hardening rate,strain hardening exponent n,and hardening capacity Hc are greatly reduced by Bi addition,mainly owing to the enhanced synergy effects of grain refinement and numerous Mg_(3)Bi_(2)precipitates.
