回归处理工艺对7050铝合金力学和晶间腐蚀性能的影响

Effect of retrogression processing on mechanical properties and intergranular corrosion of 7050 aluminum alloy

采用硬度、电导率测试、金相及透射电镜观察等手段,研究回归处理工艺对7050铝合金力学和晶间腐蚀性能的影响。研究结果表明:T6态合金硬度和强度很高,但抗晶间腐蚀能力较弱;与T6态相比,合金经较低温度长时间回归并再时效后,强度和抗晶间腐蚀性能都得到改善;合金经120℃/20 h预时效+190℃/60 min回归+120℃/24 h再时效处理后,其抗拉强度、屈服强度、伸长率和晶间腐蚀最大深度分别为593 MPa,571 MPa,10.5%和0.05 mm,具有最佳的综合性能;经190℃/60 min回归和再时效处理后,合金晶内组织与T6态的组织相似,晶界析出相粗大且不连续分布,因此,合金强度最高,抗晶间腐蚀能力最强。

The effect of retrogression processing on the mechanical properties and intergranular corrosion was investigated by means of hardness and electrical conductivity test, optical microscopy（OM） and transmission electron microscopy（TEM）. The results show that aging of 120℃/20 h leads to the highest hardness but low intergranular corrosion resistance. Compared with T6 temper, higher strength and intergranular corrosion resistance can be obtained by retrogression at lower temperature for a long time. The best properties are obtained through 190℃/60 min retrogression. After pre-aging of 120℃/20 h, retrogression of 190 ℃/60 rain, and re-aging of 120℃/24 h, the tensile strength, yield strength, elongation and maximum depth of intergranular corrosion of the studied alloy are 593 MPa, 571 MPa, 10.5% and 0.05 mm, respectively. The TEM observation results show that there are more spaced and coarser particles on the grain boundaries while the microstructures are similar to those of T6 temper in the matrix, which makes contributions to the properties.