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本文利用硬度、显微镜和透射电镜系统地研究了微量Cr对工业纯Al-5.0Zn-1.8Mg合金的沉淀过程、临界形核温度T_c~′和组织参数的影响。结果表明,Cr是促进不均匀沉淀和提高T_c~′温度的元素。低温时效(T_a≤160℃)能抑制晶界沉淀桕(GBP)、无沉淀带(PFZ)和基体沉淀相(MPt)的长大;但高温时效(T_a≥180℃)它又能促进这些参数的强烈长大。这些变化特点,可用Cr与过剩空位交互作用的双重性机理来说明。
In this paper, the effect of trace Cr on the precipitation process, critical nucleation temperature T_c ~ ’and microstructure parameters of industrial pure Al-5.0Zn-1.8Mg alloy has been studied systematically by hardness, microscopy and transmission electron microscopy. The results show that Cr is an element that promotes non-uniform precipitation and increases the temperature of T_c ~. Low temperature aging (T_a≤160 ℃) can suppress the grain boundary precipitation (GBP), no precipitation zone (PFZ) and matrix precipitation phase (MPt) growth; but high temperature aging (T_a≥180 ℃) which can promote these parameters The strong growth. These changes can be characterized by the dual mechanism of interaction between Cr and excess vacancies.