The microstructural evolution and phase transformations of a high-alloyed Al-Zn-Mg-Cu alloy (Al-8.59Zn-2.00Mg-2.44Cu,wt%) during homogenization were investigated. The results show that the as-cast microstructure mai...The microstructural evolution and phase transformations of a high-alloyed Al-Zn-Mg-Cu alloy (Al-8.59Zn-2.00Mg-2.44Cu,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 (Al2CuMg) 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℃, 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℃ for 168 h and by a two-step homogenization process conducted at 460℃ for 24 h and 475℃ for 24 h (460℃/24 h + 475℃/24 h) are in good accord with the calculated phase diagrams. It is concluded that the Al-8.59Zn-2.00Mg-2.44Cu alloy can be homogenized adequately under the 460℃/24 h + 475℃/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-2.44Cu,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 (Al2CuMg) 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℃, 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℃ for 168 h and by a two-step homogenization process conducted at 460℃ for 24 h and 475℃ for 24 h (460℃/24 h + 475℃/24 h) are in good accord with the calculated phase diagrams. It is concluded that the Al-8.59Zn-2.00Mg-2.44Cu alloy can be homogenized adequately under the 460℃/24 h + 475℃/24 h treatment.