采用透射电子显微镜 (TEM)、高分辨透射电子电镜 (HRTEM)和硬度测试等手段对轨道交通车辆用6005A合金板材的单级时效工艺, 脱溶沉淀过程中显微组织的演变以及β''相的晶体结构和取向关系进行研究分析. 结果表明: 合金经175℃时效12 h达到硬度峰值, 随后在较长时间内可以保持一个硬度平台; 在脱溶沉淀初期,合金中主要为团簇或者GP区组织, 而峰时效状态, 合金的显微组织以β''相为主;作为6005A合金中的主要强化相, 峰值过后, β''相仍不断从基体中脱溶析出并长时间存在于合金中. 此外, β''相晶体结构为C-心单斜结构,其单胞参数: a=(1.52±0.04) nm, b=0.405 nm, c=(0.67±0.04) nm,β=105.26°, 与基体的位相关系可以表示为:(010)β''//(001)Al, [200]β''//[230]Al,[002]β''//[310]Al. 6005A合金的基本析出序列可以表示为: 过饱和固溶体 (SSS)→团簇→GP区→β''相→β'相+Q'相→ β(Mg2Si)相+Q相.
The single–stage aging process, microstructure evolution during the precipitation process and crystal structure and orientation relationships between the β′′ phase and matrix were studied by means of conventional transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and hardness testing in 6005A aluminum alloy used for rail traffic vehicle. The results show that 6005A alloy can reach its peak hardness after aging at 175 for 12 h, and maintain it for a longer time. It is found that there exist clusters or GP zones in this alloy at early stage of aging and the β′′ phase at the peak–aging stage. After the peak–aging, the β′′ phase as a main strengthening phase in 6005A aluminum alloy continues being precipitated from matrix for a long time. β′′ phase has a C–centered monoclinic lattice with the lattice parameters a=(1.52±0.04) nm, b=0.405 nm, c=(0.67±0.04) nm, β=105.26?. The crystallographic orientation relationship between the β′′ phase and matrix is found as follows: (010)β′′ //(001)Al, [200]β′′ //[230]Al, [002]β′′ //[¯310]Al. And, the precipitation sequence with aging time in 6005A aluminum alloy can be described: super saturated solid solution (SSS) →clusters→GP zone→ metastable β′′ phase→ metastable β′ phase+Q′ phase→ stable β(Mg2Si) phase+Q phase.
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