7050铝合金单峰时效热处理工艺及性能研究

Study on Peak Ageing Heat Treatment Process and Properties of 7050 Aluminum Alloy

利用材料相图及性能模拟软件JMatPro对7050铝合金进行模拟计算,得到7050铝合金的TTT和CCT曲线。合金的TTT曲线整体呈“C”形,GP区、亚稳相和稳定相鼻尖温度分别为140、330、380℃,对应的孕育时间为0.002、0.007、0.200 h,η'相无析出的临界冷却速率为2℃/s。采用力学性能和电镜组织观察的方法,研究7050铝合金单峰时效热处理工艺。结果表明:当温度达到485℃时,在DSC曲线上出现吸热峰;在120℃下进行时效处理,随着时效时间的延长,合金的强度硬度持续增加,合金断后伸长率先增加后减小,时效70 h未见过时效特征,当时效8 h时,合金强度和韧性有较好配合,抗拉强度为593 MPa,屈服强度为516 MPa,断后伸长率为12.6%,试样拉伸断口均呈现穿晶韧窝型断裂与沿晶断裂的混合式断口形貌。

The TTT and CCT curves of 7050 Alloy were obtained by using material phase diagram and performance simulation software JMatPro.The TTT curve of the alloy shows a“C”shape as a whole.The tip temperatures of GP region,metastable phase and stable phase are 140,330 and 380℃,respectively.The corresponding incubation time is 0.002,0.007 and 0.200 h.The critical cooling rate of η'phase without precipitation is 2℃/s.The single peak aging heat treatment process of 7050 Alloy was studied by means of mechanical properties and microstructure observation.The results show that when the temperature reaches 485℃,the endothermic peak appears on the DSC curve,and the aging treatment is carried out at 120℃,With the extension of aging time,the strength and hardness of the alloy continue to increase,and the elongation of the alloy increases first and then decreases after aging for 70 h.When aging for 8 h,The strength and toughness of the alloy are well matched,The tensile strength and yield strength were gained at 593 MPa and 516 MPa,the elongation of the alloy reaches the maximum value of 12.6%,and the tensile fracture shows transgranular dimple fracture and intergranular fracture.Mixed fracture morphology.