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采用热力学计算与实验相结合的方法,研究了两种高强韧Al-Zn-Mg-Cu合金铸态及均匀化态的显微组织和相构成.铸态A合金主要由Mg(Zn,Al,Cu)2相和少量Al2Cu相组成,而铸态B合金仅含Mg(Zn,Al,Cu)2相.热力学计算显示,A和B两种合金的实际凝固过程介于Lever Rule和Scheil Model两种模拟结果之间,由于合金成分不同而导致的铸态A和B合金中各相含量差异与Scheil Model模拟所得到的各相摩尔分数变化规律基本一致.经常规工业均匀化处理(460℃保温24 h),铸态A和B合金中存在的Mg(Zn,Al,Cu)2或Al2Cu相均能充分回溶,并得到单相α(Al)基体,这与热力学计算所得到的AlZn-Mg-Cu四元系统在7.5%Zn条件下460℃等温相图相符合.
The microstructure and phase composition of as-cast and homogenized alloys of two high strength and toughness Al-Zn-Mg-Cu alloys were studied by means of thermodynamic calculation and experiments.The as-cast A alloys were mainly composed of Mg (Zn, Al, Cu) 2 phase and a small amount of Al2Cu phase, while the as-cast B alloy only contains Mg (Zn, Al, Cu) 2 phase.The thermodynamic calculation shows that the actual solidification process of the two alloys A and B is between Lever Rule and Scheil Model The difference of the content of each phase in the as-cast A and B alloys due to the different alloy compositions is basically the same as the change of the mole fraction of each phase obtained by the Scheil Model simulation.After conventional industrial homogenization 24 h). The Mg (Zn, Al, Cu) 2 or Al2Cu phases existing in the as-cast alloys A and B could be fully dissolved back into solution and the single phase α (Al) matrix was obtained. Mg-Cu quaternary system in 7.5% Zn 460 ℃ isothermal phase diagram is consistent.