The microstructural evolution and phase transformations of a high-alloyed Al–Zn–Mg–Cu alloy(Al–8.59Zn–2.00Mg–2.44 Cu, wt%) during homogenization were investigated. The results show that the as-cast microstructur...The microstructural evolution and phase transformations of a high-alloyed Al–Zn–Mg–Cu alloy(Al–8.59Zn–2.00Mg–2.44 Cu, wt%) during homogenization were investigated. The results show that the as-cast microstructure mainly contains dendritic α(Al), non-equilibrium eutectics(α(Al) + Mg(Zn,Al,Cu)2), and the θ(Al2Cu) phase. Neither the T(Al2Mg3Zn3) phase nor the S(Al2Cu Mg) phase was found in the as-cast alloy. The calculated phase components according to the Scheil model are in agreement with experimental results. During homogenization at 460°C, all of the θ phase and most of the Mg(Zn,Al,Cu)2 phase were dissolved, whereas a portion of the Mg(Zn,Al,Cu)2 phase was transformed into the S phase. The type and amount of residual phases remaining after homogenization at 460°C for 168 h and by a two-step homogenization process conducted at 460°C for 24 h and 475°C for 24 h(460°C/24 h + 475°C/24 h) are in good accord with the calculated phase diagrams. It is concluded that the Al–8.59Zn–2.00Mg–2.44 Cu alloy can be homogenized adequately under the 460°C/24 h + 475°C/24 h treatment.展开更多
基金supported by the Fundamental Research Funds for the Central Universities of China (No. FRF-TD-12-001)the Beijing Laboratory of Modern Traffic Metal Materials and Processing Technology
文摘The microstructural evolution and phase transformations of a high-alloyed Al–Zn–Mg–Cu alloy(Al–8.59Zn–2.00Mg–2.44 Cu, wt%) during homogenization were investigated. The results show that the as-cast microstructure mainly contains dendritic α(Al), non-equilibrium eutectics(α(Al) + Mg(Zn,Al,Cu)2), and the θ(Al2Cu) phase. Neither the T(Al2Mg3Zn3) phase nor the S(Al2Cu Mg) phase was found in the as-cast alloy. The calculated phase components according to the Scheil model are in agreement with experimental results. During homogenization at 460°C, all of the θ phase and most of the Mg(Zn,Al,Cu)2 phase were dissolved, whereas a portion of the Mg(Zn,Al,Cu)2 phase was transformed into the S phase. The type and amount of residual phases remaining after homogenization at 460°C for 168 h and by a two-step homogenization process conducted at 460°C for 24 h and 475°C for 24 h(460°C/24 h + 475°C/24 h) are in good accord with the calculated phase diagrams. It is concluded that the Al–8.59Zn–2.00Mg–2.44 Cu alloy can be homogenized adequately under the 460°C/24 h + 475°C/24 h treatment.
