时效状态对7A85高强铝合金力学性能和晶间腐蚀性能的影响

Effect of Aging Treatment on Mechanical and Intergranular Corrosion Properties of 7A85 High Strength Aluminum Alloy

摘要:

采用拉伸试验、电导率测试、晶间腐蚀实验、金相显微镜观察等方法研究不同时效制度对7A85高强铝合金的力学性能和晶间腐蚀性能的影响。研究结果表明：时效温度为110~140 ℃时，7A85铝合金的电导率随着时效温度的升高而增加，晶间腐蚀深度逐渐变浅，合金的抗晶间腐蚀性能提高；在120 ℃时效温度下，时效时间为30 h时达到第1个峰值硬度；在时效温度为120 ℃时，电导率随着时效时间的延长而增加，合金的晶间腐蚀深度减小，即合金的晶间腐蚀敏感性随时间的延长而降低。经过470 ℃/2 h +120 ℃/30 h时效工艺处理后，7A85铝合金的抗拉伸强度为710.3 MPa，屈服强度为655.46 MPa，伸长率为11.25 %，电导率为30.7 % IACS，平均晶间腐蚀深度为0.100 mm；该热处理制度可以使合金在保持良好力学性能的同时，有高的耐晶间腐蚀性能

Abstract:

The effect of different aging processes on the mechanical and intergranular corrosion properties of 7A85 high strength aluminum alloy were investigated using the methods of tensile test, conductivity test, intergranular corrosion test and metallographic microscope observation etc.. The results indicate that when the aging temperature is in the range of 110~140 ℃, the conductivity of the 7A85 aluminum alloy increases with increasing aging temperature, intergranular corrosion depth decreases gradually and the intergranular corrosion resistance of the alloy is improved. The alloy shows first peak hardness at aging time of 30 h and aging temperature of 120 ℃. At the aging temperature of 120 ℃, the conductivity increases and the intergranular corrosion depth of the alloy decreases with aging time extending, that is to say, the intergranular corrosion susceptibility of the alloy decreases with increasing aging time. After the alloy is treated with the aging process of 470 ℃/2 h +120 ℃/30 h, the tensile strength of 710.3 MPa, yield strength of 655.46 MPa, elongation rate of 11.25%, conductivity of 30.7% IACS, and average intergranular corrosion depth of 0.100 mm can be reached. The heat treatment system can make the alloy maintaining good mechanical properties as well as high intergranular corrosion resistance