抗应力腐蚀性能的影响
(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用光学显微分析、扫描电镜及透射电镜观察、慢应变速率拉伸测试等研究2056铝合金在T6、T851及T351热处理状态下的微观组织和抗应力腐蚀性能。结果表明：2056合金在T6态下，晶内析出相主要为粗大的S′相和少量粗大的含锰相，抗拉强度为445.13 MPa，晶界析出相粗大且呈非连续分布，无沉淀析出带(PFZ)为0.1~0.2 µm，应力腐蚀敏感性最大；T851态下，晶内析出相主要为细小弥散的S′相，合金具有最高的抗拉强度，达到502.01 MPa，晶界析出相呈离散状分布，PFZ较窄，约为0.02 µm，抗应力腐蚀性能优于T6态的；T351时效状态下，晶内观察到大量的位错和位错塞积以及少量GPB区，抗拉强度为469.73 MPa，介于T6和T851之间，晶界无粗大平衡相析出，无明显PFZ，抗应力腐蚀性能最好。
关键字: 2056铝合金；热处理；微观组织；应力腐蚀开裂敏感性
stress corrosion cracking of aluminum alloy 2056
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The microstructure and stress corrosion cracking (SCC) sensitivity of aluminum alloy 2056 were investigated using OM, SEM and TEM observations and slow strain rate tension testing (SSRT) in T6, T851 and T351 conditions. The results show that, in T6 aging condition, the coarsening S′ phase and small amount of coarsening Mn-containing phase are mainly observed in matrix, the ultimate strength of 2056 alloy is 445.13 MPa. The grain boundary precipitates are coarsely and sparsely distributed, and the precipitate free zone (PFZ) is 0.1−0.2 µm. In T6 condition, the stress corrosion cracking sensitivity of 2056 alloy is the largest. In T851 condition, the precipitates are high density of S′ phase in matrix, the ultimate strength of 2056 alloy is 502.01 MPa. The grain boundary precipitates are smaller obviously and discretely distributed, and the PFZ is about 0.02 µm, the corrosion resistance is higher than that in T6 condition. In T351 aging condition, the dislocation pile-up and small amount of GPB zones are observed in matrix, and there are no precipitates and PFZ in grain boundaries. In T351 condition, the ultimate strength of the 2056 alloy is between those of T6 and T851, reaching 469.73 MPa, and the alloy possesses the best resistance to SCC.
Key words: 2056 aluminum alloy; heat treatment; microstructure; stress corrosion cracking susceptibility
