The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6 Y-2.5 Zn-0.6 Zr-x Sn(x = 0, 0.2 and0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been re...The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6 Y-2.5 Zn-0.6 Zr-x Sn(x = 0, 0.2 and0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3 Y5 phase was found in 0.5% Sn-added alloy.After heat treatment at 520 °C, the transformation of the long-period stacking ordered(LPSO) phase takes place in the Mg-Y-Zn-Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of a0-Mg ? a-Mg ? 14 H and the process is the key to the transition of 18 H-LPSO to 14 H-LPSO.展开更多
Achieving high strength in Mg alloys is usually accompanied by ductility loss.Here,a novel Mg97Y1Zn1Ho1 at.%alloy with a yield strength of 403 MPa and an elongation of 10%is developed.The strength-ductility synergy is...Achieving high strength in Mg alloys is usually accompanied by ductility loss.Here,a novel Mg97Y1Zn1Ho1 at.%alloy with a yield strength of 403 MPa and an elongation of 10%is developed.The strength-ductility synergy is obtained by a comprehensive strategy,including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase(14H LPSO phase)through rare-earth Ho alloying.The lamella bimodal microstructure consists of elongated un-recrystallized(un-DRXed)coarse grains and fine dynamically-recrystallized grains(DRXed regions).The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions.The outstanding yield strength is mainly contributed by grain-boundary strengthening,18R LPSO strengthening,and fiberlike reinforcement strengthening from the nano-spaced 14H LPSO phase.The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability.展开更多
The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results ...The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results show that four phases,i.e.α-Mg,18 R long period stacking ordered（LPSO） phase,Mg24Y5 and Y-rich phase,are present in cast alloy.During ECAP,dynamic recrystallization（DRX） occurs and the diameter of DRXedα-Mg grains decreases to 0.8 μm.Moreover,precipitation of lamellar 14 H LPSO structure is developed withinα-Mg phase.Both the refinement of α-Mg grains and precipitation of 14 H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg.In addition,a simplified model describing the evolution of 18 R LPSO phase is established,which illustrates that 18 R undergoes a four-step morphological evolution with increasing strains during ECAP,i.e.original lath → bent lath → cracked lath → smaller particles.Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP,and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains,newly precipitated 14 H lamellas,18 R kinking and refined 18 R particles.展开更多
基金supported financially by the National Natural Science Foundation of China (Nos. 51774254, 51774253, 51701187, U1610123, 51674226, 51574207, and 51574206)the Science and Technology Major Project of Shanxi Province (No. MC2016-06)the Shanxi Province Science Foundation for Youths (No. 201601D021062)
文摘The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6 Y-2.5 Zn-0.6 Zr-x Sn(x = 0, 0.2 and0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3 Y5 phase was found in 0.5% Sn-added alloy.After heat treatment at 520 °C, the transformation of the long-period stacking ordered(LPSO) phase takes place in the Mg-Y-Zn-Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of a0-Mg ? a-Mg ? 14 H and the process is the key to the transition of 18 H-LPSO to 14 H-LPSO.
基金supported by the National Key Research and Development Project (2018YFE0115800, 2020YFE0202600)Youth Talent Project of China National Nuclear Corporation (CNNC2019YTEP-HEU01, CNNC2021YTEP-HEU01)+4 种基金the NSFC Funding (51701051, 52001083, 52171111, U2141207)China Postdoctoral Science Foundation Funded Project (2019T120255)Natural Science Foundation of Heilongjiang (LH2019E030)Heilongjiang Touyan Innovation Team Programthe supports from the U.S. National Science Foundation [DMR-1611180 and 1809640] with the program directors, Drs. Judith Yang, Gary Shiflet, and Diana Farkas.
文摘Achieving high strength in Mg alloys is usually accompanied by ductility loss.Here,a novel Mg97Y1Zn1Ho1 at.%alloy with a yield strength of 403 MPa and an elongation of 10%is developed.The strength-ductility synergy is obtained by a comprehensive strategy,including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase(14H LPSO phase)through rare-earth Ho alloying.The lamella bimodal microstructure consists of elongated un-recrystallized(un-DRXed)coarse grains and fine dynamically-recrystallized grains(DRXed regions).The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions.The outstanding yield strength is mainly contributed by grain-boundary strengthening,18R LPSO strengthening,and fiberlike reinforcement strengthening from the nano-spaced 14H LPSO phase.The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability.
基金the financial support from the Natural Science Foundation of Jiangsu Province(No.BK20160869)the Nantong Science and Technology Project(No.GY12015009)+1 种基金the Fundamental Research Funds for the Central Universities(No.2015B01314)the National Natural Science Foundation of China(No.51501039)
文摘The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results show that four phases,i.e.α-Mg,18 R long period stacking ordered（LPSO） phase,Mg24Y5 and Y-rich phase,are present in cast alloy.During ECAP,dynamic recrystallization（DRX） occurs and the diameter of DRXedα-Mg grains decreases to 0.8 μm.Moreover,precipitation of lamellar 14 H LPSO structure is developed withinα-Mg phase.Both the refinement of α-Mg grains and precipitation of 14 H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg.In addition,a simplified model describing the evolution of 18 R LPSO phase is established,which illustrates that 18 R undergoes a four-step morphological evolution with increasing strains during ECAP,i.e.original lath → bent lath → cracked lath → smaller particles.Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP,and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains,newly precipitated 14 H lamellas,18 R kinking and refined 18 R particles.
