Effect of natural aging on microstructure and mechanical properties of the 6061 aluminum alloy was investigated by tensile test and transmission electron microscopy. The results show that a few tiny spherical GP zones precipitated from the matrix of aluminum alloy after natural aging for one month. A great quantity of GP zones and lath-like β-Mg2 Si equilibrium phase precipitated after artificial aging for 6 h. More precipitate phases were found in the alloy after natural aging for one month at first then artificial aging when compared with the alloy after direct artificial aging. With the prolongation of natural aging time, strength of the aluminum alloy gradually increased and elongation gradually decreased. The properties tended to be stable after one month, that the tensile and yield strength, elongation were 217. 27 MPa, 130.78 MPa and 18. 40％, respectively. Good comprehensive properties could be obtained after natural aging for one month and artificial aging for 4 h, that the tensile and yield strength, elongation were 273. 72 MPa, 228. 63 MPa and 11.16％. Comparing with the alloy after direct artificial aging, the tensile strength and yield strength decreased slightly, and the elongation increased by 11.6％.%采用拉伸试验、透射电镜分析等方法研究了自然时效对6061铝合金显微组织和力学性能的影响.结果表明:自然时效1个月后,铝合金基体中析出少量极细小的球状GP区,而人工时效6h则析出大量GP区和板条状β-Mg2Si平衡相;自然时效1个月后再进行人工时效的析出相较直接进行人工时效态的少;随着自然时效时间的延长,铝合金强度逐渐升高,伸长率逐渐降低,1个月后性能趋于稳定,抗拉强度和屈服强度分别为217.27和130.78MPa,此时具有较高的伸长率,为18.40%;自然时效1个月后再进行4h人工时效可获得较好的综合性能,抗拉强度、屈服强度和伸长率分别为273.72MPa,228.63MPa和11.16%,与直接进行人工时效的相比,抗拉强度、屈服强度稍有下降,但伸长率提高了11.6%.
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