时效处理对7A55铝合金微观组织和性能的影响

系统研究了时效处理对7A55铝合金微观组织演变和性能的影响。测试了其显微硬度、力学性能和电化学腐蚀性能,表征了透射组织和腐蚀形貌。试验结果表明:固溶处理后的7A55试验铝合金,具有高的硬化响应速率。经160 ℃×12 h时效处理后,显微硬度达到峰值,由固溶处理后的56 HV0.5提高到87 HV0.5,提高了55.36%,且前期的硬度升高速率极快。预时效(PA)处理抑制了试验7A55铝合金的自然时效(NA)效应,提升了烘烤硬化(BH)响应。经BH处理后,PA+NA态的屈服强度明显提升,达到475 MPa,硬化增量达到190 MPa,提高了66.67%,伸长率降低为12.5%。PA+NA+BH状态下,析出相粒子尺寸更为细小,粒子直径在10~15 nm范围,且分布均匀。PA+NA+BH态的合金腐蚀电位最高,为－1.032 V(vs SCE),腐蚀坑数量最少,平均腐蚀深度约为33 μm,最不易被腐蚀。

Influence of aging treatment on microstructure and properties of 7A55 aluminum alloy

Influence of aging treatment on microstructure evolution and properties of 7A55 aluminum alloy was investigated. The microhardness, mechanical properties and electrochemical corrosion behavior were tested. The TEM microstructure and corrosion morphology were characterized. The results indicate that the experimental 7A55 aluminum alloy after solution treatment has higher hardening rate. After aging at 160 ℃ for 12 h, the hardness reaches the peak (87 HV0.5) from 56 HV0.5 in the solution treated state, i.e., increased by 55.36%, and the hardening rate in early aging stage is very high. Pre-aging (PA) treatment inhibits the natural aging (NA) effect and improves the bake hardening (BH) response. The yield strength under PA+NA state after BH treatment reaches 475 MPa with an increment of 190 MPa, which improves 66.67%, and the elongation reaches 12.5%. The precipitated particles under PA+NA+BH state are finer and uniformly distributed, with the diameter in the range of 10-15 nm. The PA+NA+BH state alloy has the highest corrosion potential (－1.032 V, vs SCE), the least corrosion pits and the best corrosion resistance, with the average corrosion depth being about 33 μm.