晶粒组织对Al-Zn-Mg-Cu-Cr合金淬火敏感性的影响

摘要

The effect of grain structure on quench sensitivity of an Al−Zn−Mg−Cu−Cr alloy was investigated by hardness testing, optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and scanning transmission electron microscopy. The results show that with the decrease of quenching rate from 960 °C/s to 2 °C/s, the hardness after aging is decreased by about 33%for the homogenized and solution heat treated alloy (H-alloy) with large equiaxed grains and about 43%for the extruded and solution heat treated alloy (E-alloy) with elongated grains and subgrains. Cr-containing dispersoids make contribution to about 33% decrement in hardness of the H-alloy due to slow quenching; while in the E-alloy, the amount of (sub) grain boundaries is increased by about one order of magnitude, which leads to a further 10%decrement in hardness due to slow quenching and therefore higher quench sensitivity.%采用硬度测试、光学显微镜、X-射线衍射、扫描电镜、透射电镜和扫描透射电镜等手段研究了晶粒组织对Al−Zn−Mg−Cu−Cr合金淬火敏感性的影响。结果表明：淬火速率从960°C/s减小至2°C/s时，均匀化及固溶后合金(H-合金)时效后的硬度下降了约33%，而挤压及固溶后合金(E-合金)时效后的硬度下降了约43%。H-合金中有粗大等轴状晶粒，E-合金中有拉长的变形晶粒及亚晶粒。慢速淬火H-合金硬度下降33%是由含Cr弥散粒子引起的；E-合金中(亚)晶界的数量增加了大约一个数量级，导致慢速淬火试样硬度的下降幅度进一步增加了10%，淬火敏感性更高。