通过硬度测试、扫描电镜、透射电镜研究淬火速率对Al-Zn-Mg-Cu-Cr合金挤压棒材组织及硬度的影响.结果表明:淬火速率低于100℃/s时,硬度开始明显下降;2℃/s淬火时,硬度下降了43%.淬火速率低于100℃/s时,随着淬火速率降低,冷却过程中(亚)晶界及晶内弥散粒子处非均匀形核析出η平衡相的数量和尺寸明显增加,时效强化效果明显降低.相同淬火速率时,晶内η平衡相尺寸大于晶界η平衡相尺寸.在所研究的淬火速率范围内建立起硬度值与η平衡相面积分数间的定量关系.
The effect of quenching rate on microstructure and hardness of Al-Zn-Mg-Cu-Cr alloy extruded bar was studied by hardness test, scanning electron microscopy and transmission electron microscopy.The results show that at quenching rate below 100℃/s, during the cooling process, the hardness begins to fall significantly;and it decreases by 43% at the quenching rate of 2℃/s.At quenching rate below 100℃/s, the number and size of equilibrium η phase heterogeneously nucleated at(sub)grain boundaries and on dispersoids inside grains increase obviously with the decrease of quenching rate, leading to greatly reduced age-hardening response.At the same quenching rate, the equilibrium η phase inside grains is larger than that at grain boundaries.In the range of the studied quenching rates, a quantitative relationship between hardness and equilibrium η phase area fraction has been established.
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