稀土元素对轧制Mg–Zn–Zr合金板材微观组织和力学性能的影响

Effect of Rare Earth(RE)on Microstructure and Mechanical Property of Rolled Mg-Zn-Zr Alloy Plate

目的为了使Mg-Zn-Zr合金在热加工过后具有良好的力学性能及变形各向同性,在Mg-2Zn-0.5Zr合金中添加不同含量的稀土元素,研究稀土元素对Mg-2Zn-0.5Zr合金轧制后微观组织和力学性能的影响规律,以解决变形镁合金织构强、变形各向异性强的问题。方法通过添加不同含量(0.2%和0.8%,质量分数)的混合稀土元素,采用轧制的方法制备镁合金板材。通过SEM(扫描电子显微镜)、EDS(能谱仪)、EBSD(背散射电子衍射)和电子万能试验机等对镁合金板材的成分、微观组织、织构以及拉伸过程中的应力-应变曲线进行分析。结果混合稀土元素的添加会明显提高Mg-Zn-Zr合金板材的轧制成形性,可以起到细化晶粒、弱化轧制织构的作用,能够提高材料的伸长率并改善力学性能的各向异性。混合稀土元素会与Mg、Zn在晶界处形成第二相,但并不会影响稀土元素的织构弱化效果。与较低稀土元素(质量分数为0.2%)时相比,当混合稀土元素含量较高时(质量分数为0.8%),合金材料的力学性能各向异性更优,这主要是由于添加较多的稀土元素,形成了{4333}织构,使添加较多稀土元素的合金材料的织构强度更强。结论随着混合稀土元素的添加,Mg-2Zn-0.5Zr合金的织构强度先降低后升高,并且随着材料织构弱化,材料力学性能的各向异性减弱。

The work aims to add different contents of rare earth elements into Mg-2Zn-0.5Zr alloy,in order to make Mg-Zn-Zr alloy have good mechanical properties and deformation isotropy after hot working and study the effect of rare earth elements on the microstructure and mechanical properties of Mg-2Zn-0.5Zr alloy after rolling,so as to solve the problem of strong texture and strong deformation anisotropy of wrought magnesium alloy.Magnesium alloy plates were prepared by rolling with different contents of mixed rare earth elements(0.2%and 0.8%,wt.%).The composition,microstructure,texture and stress-strain curve in the tensile process of magnesium alloy plates were analyzed by SEM,EDS,EBSD and electronic testing machine.The addition of mixed rare earth elements significantly improved the rolling formability of Mg-Zn-Zr alloy plates,refined grain size,weakened rolling texture,increased material elongation,and improved mechanical anisotropy.Secondly,mixed rare earth elements formed a second phase with Mg and Zn at grain boundaries,but did not affect the texture weakening effect of rare earth elements.Finally,when the mixed rare earth element content is high(0.8%),the anisotropy of the mechanical properties of the alloy material was stronger than that when the rare earth element content was low(0.2%).This was mainly caused by the formation of {4333} texture after addition of more rare earth elements,making the texture strength of the alloy material with more rare earth elements stronger than that of the alloy with less rare earth elements.With the addition of mixed rare earth elements,the texture of Mg-2Zn-0.5Zr alloy decreases firstly and then increases,and as the texture weakens,the anisotropy of the mechanical property of material weakens.