材料期刊网

研究了Al--5.2Cu--0.4Mg--1.02Ag合金在不同时效制度下的力学性能和显微组织, 并详细分析了合金的主要析出相Ω的形核与粗化, 同时提出了浓度台阶粗化机制. 结果表明: 合金的主要强化相是Ω相和θ'相. 欠时效时出现了大量细小的Ω相和少量的θ'相; 峰时效时Ω相和θ'相的体积分数大大增加, 且Ω相与基体呈半共格关系; 过时效时出现了球状的平衡θ'相, Ω相略为长大, 而θ'相的长度和厚度明显增大. Mg/Ag原子簇是时效初期Ω相的形核核心; Mg, Ag和Cu的浓度差异引起的台阶迁移是Ω相粗化的驱动力. 由于Mg和Ag原子在Ω相与基体界面存在时降低了晶格的畸变能, 使得Cu原子向Ω相迁移的速率受到限制, 因此Ω相能够在长时间下保持片状而不发生共格失稳.

The mechanical properties and microstructures of Al–5.2Cu–0.4Mg–1.02Ag alloy during different aging processes were studied. The nucleation and coarsening of the main precipitation Ω phase were investigated, and the concentration ledge coarsening mechanism was proposed. The results show that the main precipitated phases are Ω phase and θ‘ phase A large number of fine Ω phase precipitates but a small amount of θ’ phase precipitates are found in the underaged alloy At peak–aging, the volume fraction of both Ω phase and θ‘ phase increases significantly and Ω phase issemi–coherent with the matrix. The equilibrium θ phase is found in subsequent overaging. During this time, Ω phase grows slowly but θ’ phase quickly both in length and thickness. Each of Mg/Ag co–clusters is used as a nucleation site of Ω phase in initial aging stage. The driving force for Ω phase coarsening comes from ledge migration caused by the atomic concentration difference of Mg, Ag and Cu. Since the segregation of Ag and Mg atoms in the interface between Ω phase and matrix reduces the misfit energy of lattice, the velocity of Cu atom moving to Ω phase is limited and Ω phase can keep its platelet shape well and the cohesion destabilization does not occur in long term aging.