7A55铝合金厚板的微观组织和性能不均匀性

Inhomogeneity of microstructure and properties of 7A55 aluminum alloy thick plate

采用金相显微镜、扫描电镜、透射电镜、织构分析、硬度、电导率、拉伸测试等实验手段研究7A55铝合金厚板T6态微观组织与性能沿厚度方向的演变规律。研究结果表明:在板材的厚度方向上,板材的微观组织和硬度、电导率、强度、织构等存在不均匀性。从板材表层到心部,其再结晶分数依次降低,残余第2相体积分数、电导率和强度依次升高,表层硬度比心部的高,1/4层的硬度最高。心部含有最多的轧制型织构为铜织构{112}?111?,黄铜织构{011}?211?和S织构{123}?634?,表层含有最多的再结晶织构为{001}?100?。轧制型织构具有更大的泰勒因子M,对强度贡献更大,表层的再结晶严重削弱了其力学性能,影响各层力学性能差异的主要因素是再结晶及织构。

The microstructure and properties evolution of 7A55 aluminum alloy thick plate along the thickness direction were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, hardness, conductivity and tensile tests. The results show that the microstructure, texture and mechanical properties in different layers along the thickness direction are inhomogeneous. From the surface to the center layer,the fraction of recrystallization decreases while the volume fraction of coarse particles and conductivity as well as strength increase. The hardness of the surface layer is higher than that of the center layer, and the hardness of 1/4 layer is the highest. The center layer of the plate has more rolling texture than surface, such as copper texture{112}〈111〉, brass texture{011}〈211〉 and S texture{123}〈634〉 while surface layer has more recrystallization texture, such as {001}〈100〉. The Taylor factor M of rolling texture is larger and contributes more to the strength, and the high fraction of recrystallization sharply decreases the strength of the surface layer. Recrystallization and texture are the main factors of inhomogeneity in mechanical properties.