Er元素对定向凝固Al-Zn-Mg-Cu-Zr合金微观组织和共晶相形貌的影响

Effects of Er on the Microstructure and Eutectic Phase Morphology of Directionally Solidified Al-Zn-Mg-Cu-Zr Alloys

采用定向凝固方法制备了Al-Zn-Mg-Cu-Zr-xEr(x=0,0.1,02,05,质量分数,%)4种合金棒。利用光学显微镜(OM)、电子探针(EPMA)、能谱分析(EDS)和其他方法研究了铸态合金的微观组织和第二相形貌。结果表明:Er元素能增加Al-Zn-Mg-Cu-Zr合金定向凝固组织的枝晶数量,并能减小合金的一次枝晶臂间距和二次枝晶臂间距。适量Er元素能减少合金第二相的含量并有利于形成圆形第二相。生成的Al_(8)Cu_(4)Er相会降低T相(AlZnMgCu)中的Cu含量,起到圆润T相边界的作用,改变了T相的形貌和内部结构,并且Al_(8)Cu_(4)Er相能充当T相的形核位置,使得一部分T相围绕该相生长。Er的添加会提高合金的显微硬度。

Four alloy rods of Al-Zn-Mg-Cu-Zr-xEr(x=0,0.1,0.2,0.5,wt%)were prepared by directional solidification.The microstructure and second phase morphology of alloys were investigated by optical microscopy(OM),electron probe micro-analysis(EPMA),energy dispersive spectrometer(EDS)and other methods.The results indicate that Er element can increase the number of dendrites in the directional solidification structure of Al-Zn-Mg-Cu-Zr alloy,and reduce the primary dendrite arm spacing and secondary dendrite arm spacing of the alloy.A proper amount of Er element can reduce the content of second phase in the alloy and increase the tendency to form round second phase.The formation of Al_(8)Cu_(4)Er phase can reduce the Cu content in the T phase(AlZnMgCu phase),which plays a role of rounding the boundary of the T phase,and can change the morphology and internal structure of the T phase.The Al_(8)Cu_(4)Er phase serves as the nucleation position of the T phase,and part of the T phase grows around this phase.The addition of Er can improve the microhardness of the alloy.