先进高强韧Al-Zn-Mg-Cu合金凝固和均匀化组织及相构成

Microstructure and phase components of as-cast and homogenized advanced Al-Zn- Mg- Cu alloys with high strength and toughness

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 components of as-cast and homogenized Al- Zn- Mg- Cu alloys with high strength and toughness were studied by combining thermodynamic calculation with experiments. It is found the secondary phases presented in as-cast alloy A are Mg（Zn,Al,Cu） 2 and a small amount of Al2 Cu; however, only Mg（Zn,Al,Cu） 2 is found in as-cast alloy B. Thermodynam-ic calculation results show that the real solidification paths of alloys A and B fall between simulations by the Lever rule and the Scheil model, and the differences in content of phases in the two as-cast alloys are consistent with the regularity of the calculated mole fraction of phases formed after solidification in the Scheil model. Mg（Zn,Al,Cu） 2 or Al2 Cu phase in as-cast alloys A and B can be dissolved completely after conventional homogenization treatment （holding at 460 ℃ for 24 h）, single α（Al） phase can be obtained, and this is consistent with the calculated isothermal section of the Al- Zn- Mg- Cu phase diagram with 7. 5% Zn at 460 ℃ .