采用末端淬火实验、光学显微镜、扫描电子显微镜、透射电子显微镜和差示扫描量热法, 研究了时效制度对7055铝合金厚板淬透性的影响. 结果表明: 人工时效前进行长时间的自然时效可提高板材的淬透性, 自然时效和人工时效的淬透深度分别约为78和45 mm, 而自然+人工时效的淬透层深度可达100 mm. 冷却速率减小时, 析出了粗大的$\eta$平衡相, 溶质和空位浓度降低, 时效后的 η'沉淀强化相数量减少, 尺寸增加, 因此硬度降低. 人工时效前的长时间自然时效有利于慢速冷却处形成稳定的 GP区, 最终得到数量更多、分布更均匀弥散、尺寸更细小的$\eta^{\prime}$ 沉淀强化相, 硬度升高, 提高了淬透性.
The influence of aging on the hardenability of 7055 aluminum alloy thick plate was investigated by means of end-quench test, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the hardenability can be improved by long time natural aging before artificial aging. The hardened depth is about 78 mm after natural aging and only about 45 mm after artificial aging, but increased to be about 100 mm after natural and artificial aging. During slow quenching, the coarse η equilibrium phase forms, and the solute concentration and vacancy concentration are decreased, which lead to larger and fewer η' hardening precipitates, thus lower hardness after aging. The long time natural aging before artificial aging is favorable for formation of stable GP zones at slowly-cooled locations, and consequently more amount of dispersed and fine η' hardening precipitates, which give rise to higher hardness and simultaneously better hardenability.
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