均匀化处理对7A52铝合金组织和性能的影响

Effect of homogenization treatment on microstructure and properties of 7A52 aluminum alloys

采用硬度、电导率测量、金相和高温原位X射线衍射分析技术研究不同均匀化处理条件下7A52铝合金组织与性能的变化规律,着重讨论不同均匀化处理条件下合金的物相组成及其演变、基体固溶体固溶度的变化与合金硬度和电导率的关系。研究结果表明:铸态合金由-αAl过饱和固溶体及少量平衡相MgZn2组成;在均匀化处理过程中,铸态合金显微组织结构发生了2个方面的变化:一方面,在300℃以下均匀化,过饱和固溶体分解,析出MgZn2平衡相;在400℃以上均匀化,上述平衡相又逐步回溶到基体固溶体中;另一方面,在400℃以上均匀化,铸态合金枝晶组织和枝晶间粗大的平衡相随均匀化温度的升高而逐步消失,与此同时,铸态合金的硬度先降低然后升高,电导率则先升高然后降低。这种性能的变化与铸态合金的组织结构变化一一对应。7A52合金铸锭适宜的均匀化处理工艺为470℃/24 h。

The microstructures and properties of 7A52 aluminum alloy under different homogenization conditions were studied by hardness test, electrical-conductivity measurement, optical metallography and high temperature in-situ X-ray diffraction. Especially, the evolution of microstructures and relations between solid solubility and both hardness and conductivity were investigated. The results show that the cast alloy is composed of a-Al supersaturated solid solution and minor equilibrium phase. Two changes take place in homogenization： supersaturated solid solution changes into MgZn2 equilibrium phase at 300℃ equilibrium phases are dissolved into matrix when the homogenization temperature is higher than 400℃. On the other hand, coarsened equilibrium phase in the cast alloy gradually disappears. The hardness decreases at first and then increases, and the conductivity increases at first and then decreases. The proper homogenization condition is 470℃/24 h.