时效制度对6156铝合金力学性能及腐蚀性能的影响

Effect of Aging Treatments on the Mechanical Properties and Corrosion Behavior of 6156 Aluminum Alloy

通过常规拉伸、慢应变速率拉伸和晶间腐蚀实验研究了T6及双级时效处理对6156铝合金力学性能与腐蚀性能的影响,并采用透射电镜(TEM)观察了析出相特征。结果表明:6156合金在T6欠时效状态下晶内析出相主要为GP区,晶界无明显析出相;T6峰时效晶内析出相主要为β″相,出现少量的Q′相,晶界析出物呈连续分布,合金虽然具有最高强度,但晶间腐蚀严重,应力腐蚀敏感性最大;随时效时间延长,Q′相增多并逐渐粗化,晶界析出物粗大非连续分布;T78时效态晶内析出大量的Q′相,晶界析出相球化且析出相之间的间距增大,呈断续分布,无沉淀析出带(PFZ)变宽,因此相比T6态而言T78状态合金强度损失不大而耐蚀性得到明显提高。

The effects of aging treatments on the mechanical properties and corrosion behavior of 6156 A1 alloy were investigated by means of hardness measurement, conventional tensile test, slow strain rate tensile tests （SSRT） and intergranular corrosion test. The microstructures were observed with TEM. The results show that in T6 under-aging （T6UA） condition the precipitates are GP zones with high density in matrix, and no distinct grain boundary precipitates are observed. In T6 peak-aging （T6PA） condition the precipitates are β″ phase with high density and small amount of Q＇ phase in matrix, the grain boundary precipitates are continuously distributed. The strength of T6 peak-aged 6156 alloy is the highest, however it has the serious tendency to intergranular corrosion and very high sensitivity to stress corrosion crack. With the aging time increasing, Q＇ phase increases and coarsens, the grain boundary precipitates are coarsened obviously and sparsely distributed, precipitate free zone （PFZ） appears. In T78 conditions, there are plenty of Q＇ precipitates in matrix, and the coarse and isolate precipitates present in grain boundaries, and the PFZ is broaden. So the corrosion resistance is obviously improved while tensile strength is a little decreased.