固溶工艺对高强韧211Z.X铝合金组织和性能的影响

Microstructure and Mechanical Performance of 211Z.X Aluminum alloy with High Strength & Toughness under Different Solution Process Parameters

采用组织分析、布氏硬度及拉伸性能测试、断口形貌的扫描电镜(SEM)和能谱分析(EDS)等方法,研究了不同的固溶工艺对211Z.X新型高强韧铝合金的显微组织、力学性能及断裂行为的影响规律。结果表明,当固溶温度范围为520~550℃,固溶时间从12~20 h时,随固溶温度的上升或保温时间的延长,合金中粗大第二相逐渐回溶入基体、数量逐渐减小,基体固溶强化增强,淬火后基体的过饱和度增大、硬度增加;导致时效过程从基体中弥散析出的细小第二相数量增加,合金的强度提高、塑性下降;合金断裂时裂纹萌生位置从粗大第二相处转变为溶质原子偏聚区(G.P zones)和铸造微孔处。但是,当粗大第二相回溶完全后,继续升高温度或延长保温时间,晶粒将急速长大,出现过烧导致晶界弱化,拉伸时易发生沿晶开裂使合金的强塑性降低。530℃×16 h固溶处理时211Z.X铝合金的强塑性匹配最好。

The influence of different solution process parameters on microstructure, mechanical properties and fracture behavior of 211Z.X new type aluminum alloy with high strength and toughness was researched with methods of microstructural analyzing, Brinell hardness test, tensile properties test, analyzing of fractographical scanning electronic microscopy(SEM) and energy dispersive spectrometer(EDS). The results indicated that when quenching temperature was ranging from 520 to 550 ℃ and the time was ranging from 12 to 20 h, the volume of large secondary phases gradually decreased and dissolved into the matrix with the increase of solution temperature or time, which induced the increase of solid solubility and saturation of the matrix. A large number of small precipitates would precipitate from the matrix during aging process, which would lead to the increase of strength. Meanwhile, the crack initiation site would change from the large second phase to similar G.P zones and casting holes owing to dissolving of large second phases. However, if the temperature or the time increased further when large second phases dissolved completely, the grains grew larger and the over-burning would widen grain boundaries, which resulted in the decrease in both strength and ductility owing to intergranular crack during tensile testing. The optimum solution process of 211Z.X aluminum alloy was to perform solution treatment at 530 ℃ for 16 h.