添加微量Sc、Zr对超高强铝合金微观结构和性能的影响

摘要

The Al−9Zn−2.8Mg−2.5Cu−xZr−ySc alloys (x=0, 0.15%, 0.15%; y=0, 0.05%, 0.15%), produced by low-frequent electromagnetic casting technology, were subjected to homogenization treatment, hot extrusion, solution and aging treatment. The effects of minor Sc and Zr addition on microstructure, recrystallization and properties of alloys were studied by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that Sc and Zr addition can refine grains of the as-cast alloy by precipitation of primary Al3(Sc,Zr) particles formed during solidification as heterogeneous nuclei. Secondary Al3(Sc,Zr) precipitates formed during homogenization treatment strongly pin the movement of dislocation and subgrain boundaries, which can effectively inhibit the alloys recrystallization. Compared with the alloy without Sc and Zr addition, the Al−Zn−Mg−Cu−Zr alloy with 0.05%Sc and 0.15%Zr shows the increase in tensile strength and yield strength by 172 MPa and 218 MPa, respectively. Strengthening comes from the contributions of precipitation, substructure and grain refining.%采用低频电磁铸造技术制备Al−9Zn−2.8Mg−2.5Cu−xZr−ySc (x=0,0.15%,0.15%；y=0,0.05%,0.15%)合金，借助金相显微镜、扫描电镜、透射电镜、力学性能测试等手段分别对其均匀化、热挤压态、固溶态和时效态的组织与性能进行对比分析。结果表明：添加微量Sc和Zr，会在凝固过程中形成初生Al3(Sc,Zr)，可显著细化合金铸态晶粒；均匀化时形成的次生 Al3(Sc,Zr)粒子可以强烈钉扎位错和亚晶界，有效抑制变形组织的再结晶，显著提高合金的力学性能。与不含Sc、Zr的合金相比，含0.05%Sc和0.15%Zr的合金经固溶处理和峰值时效处理后其抗拉强度和屈服强度分别提高172 MPa和218 MPa，其强化作用主要来自含Sc、Zr化合物对合金起到的亚结构强化、析出强化和细晶强化。