高Zn含量对挤压Mg-Zn-Ca-Y镁合金微观组织和力学性能的影响

Effect of high Zn addition on microstructure and mechanical properties of extruded Mg-Zn-Ca-Y magnesium alloy

制备不同Zn质量分数的Mg-x Zn-0.3%Ca-0.1%Y(x=7%,10%,13%)挤压镁合金,研究Zn质量分数对合金组织和力学性能的影响。研究结果表明:随着Zn质量分数增加,挤压合金的第二相体积分数增加,平均晶粒粒径和再结晶程度均先减小再增大,织构强度(极密度)则先升高再降低。与Zn质量分数分别为7%和13%的合金相比,Mg-10%Zn-0.3%Ca-0.1%Y合金在微观组织上具有最小的平均晶粒粒径(2.89μm)、最低的再结晶程度(60.4%)和最强的织构(极密度为9.77),其晶粒分布具有双峰组织特点,且带状第二相更纤长,具有大量纳米级I相析出且分布均匀,与另外2种合金在第二相的分布上存在明显差异。Mg-10%Zn-0.3%Ca-0.1%Y合金在宏观上表现为最优的综合力学性能:屈服强度为215.6 MPa,抗拉强度为326.1 MPa,伸长率为27.3%。细晶强化是其力学性能优异的主要原因,织构强化和第二相强化的影响相对较小,而合金晶粒细小则主要由Zn质量分数变化引起的第二相分布差异所致。

With the preparation of Mg-x Zn-0.3% Ca-0.1%Y(x=7%,10%,13%) extruded magnesium alloys with different Zn addition,and the effect of Zn addition on the structure and mechanical properties of the alloy was studied.The results show that with the increase of Zn mass fraction,the volume fraction of the second phase of the extruded alloy increases,the average grain size and the degree of recrystallization both decrease and then increase,and the texture intensity(pole density) first increases and then reduces.The Mg-10% Zn-0.3% Ca-0.1%Y alloy has the least average grain size(2.89 μm),the lowest degree of recrystallization(60.4%) and the strongest texture(pole density is 9.77) in the microstructure.The grain distribution of Mg-10%Zn-0.3%Ca-0.1%Y alloy has the characteristics of bimodal structure,and the band-shaped second phase is longer and has a large number of nanolevel I phases precipitated and uniformly distributed,which is obviously different from those of the other two alloys.The Mg-10% Zn-0.3% Ca-0.1%Y alloy shows the best comprehensive mechanical properties in the macroscopic view as follows:the yield strength is 215.6 MPa,the tensile strength is 326.1 MPa,and the elongation is 27.3%.Fine grain strengthening is the main reason for the excellent mechanical properties of the alloy.The effects of texture strengthening and second phase strengthening are relatively small,while the alloy’s fine grain size is mainly caused by the second phase distribution difference caused by the change of Zn addition.