回归加热速率对7050铝合金组织及抗腐蚀性能的影响

Effect of retrogression heating rate on the microstructure and corrosion resistance of aluminum alloy 7050

采用电导率、抗腐蚀性能测试及透射电镜观察等手段,研究了回归再时效处理过程中回归加热速率(340,57及4.3℃.min-1)对7050铝合金组织与抗晶间腐蚀和应力腐蚀性能的影响.研究发现,回归加热速率对7050铝合金的抗腐蚀性能有显著的影响,在顾及合金的综合力学性能的情况下,中等回归加热速率能使合金具有较好的抗腐蚀性能.7050铝合金在中速(57℃.min-1)回归加热条件下,经适当地回归再时效处理后,晶间腐蚀最大深度为50μm,等级为3级,比在340℃.min-1和4.3℃.min-1回归加热速率条件下具有更好的抗腐蚀性能,其晶界析出相为较粗大的非连续颗粒,并有较宽的无沉淀析出带.

The effect of retrogression heating rate（340,57,and 4.3 ℃·min^-1）on the microstructure,intergranular corrosion and stress corrosion resistance of aluminum alloy 7050 was investigated using electrical conductivity,intergranular corrosion and stress corrosion cracking testing and transmission electron microscopy（TEM）.The results show that retrogression heating rate affects significantly the corrosion resistance of the alloy treated by retrogression and reaging process,and that under the condition of considering the comprehensive mechanical properties,the alloy has a better corrosion resistance at the medium rate.After retrogression and reaging at the retrogression heating rate of 57 ℃·min^-1,the maximum intergranular corrosion depth of the alloy is 50 μm,i.e.Grade 3,which is shallower than those at the retrogression heating rates of 340 ℃·min^-1 and 4.3 ℃·min^-1.It is found that there are wider precipitate free zones and coarser discontinuous precipitates at grain boundaries.