Er、Zr及热处理对高锌铝合金组织和力学性能的影响

Effect of Er,Zr and Heat Treatment on Microstructure and Mechanical Properties of High Zinc Aluminum Alloy

以Al-30Zn-3Cu-2.5Si高锌铝基合金为研究对象,探究稀土元素Er、Zr对铸态及热处理态合金组织和力学性能的影响,并分析和探讨了其作用机理。结果表明,当添加0.10%(质量分数,下同)Er和0.10%Zr元素后能够明显地细化合金晶粒,平均晶粒尺寸由74.28μm减小至60.01μm,且α-Al晶粒转变为细小的等轴晶。稀土元素Er、Zr的添加会在合金内部形成Al3(Er,Zr)细小的粒子并能够起到钉扎位错的作用,从而提高合金的力学性能。添加Er、Zr后,铸态合金的抗拉强度由未添加稀土元素的323.01 MPa提高到了358.29 MPa,提升了10.93%;屈服强度由309.33 MPa提高到了315.00MPa,提升了1.83%;延伸率基本未发生变化。合金经固溶时效热处理强化后,添加稀土元素合金的抗拉强度为449.48 MPa,屈服强度为408.51 MPa,比铸态合金分别提高了25.45%、29.68%。粗大的第二相存在于晶界处,导致合金的延伸率仍较差。

Al-30Zn-3Cu-2.5Si high Zn Al-based alloy was taken as the research object,the effects of Er and Zr on the microstructure and mechanical properties of as-cast and heat-treated alloys were investigated,and the action mechanism was analyzed and discussed.The results show that the grain size of the alloy can be obviously refined by adding 0.10wt%Er and 0.10wt%Zr,the average grain size is reduced from 74.28μm to 60.01μm,and the grains ofα-Al are changed into fine equiaxed grains.The addition of rare earth elements Er and Zr can form fine particles of Al3(Er,Zr)in the alloy and pin dislocations to improve the mechanical properties of the alloy.After adding Er and Zr,the tensile strength of as-cast alloy increases from 323.01 MPa to 358.29 MPa,which increases by 10.93%;the yield strength increases from 309.33 MPa to 315.00 MPa,which increases by 1.83%;the elongation barely changes.The tensile strength and yield strength of the alloy strengthened by solution-aging heat treatment are 449.48 and 408.51 MPa,which are 25.45%and 29.68%higher than those of the as-cast alloy,respectively.The coarse second phase exists at the grain boundary,which results in the poor elongation of the alloy.