【摘要】 研究了双级时效的预时效阶段及高温短时回归时效处理对AA7050合金组织和性能的影响。结果表明,AA7050合金时效硬化效果明显,预时效温度越高,硬化速率越快;在不高于135℃下时效,具有较好的抗过时效能力。135℃下预时效12 h后,晶内组织以GP区为主,且晶界平衡相细小连续,无明显晶界无析出带,合金强度处于亚峰值状态。170℃高温二级时效处理时,随时效时间延长,合金强度先上升后下降;时效2 h时,综合力学性能最佳,晶内主要强化相为GP区和η’相,晶界为不连续的η相,伴随10～20 nm的晶界无析出带,随二级时效时间延长,晶内η’相大量向η相转化,强度迅速下降。更多还原

【Abstract】 Effect of pre-aging parameters of two-step aging and short time retrogression aging at high temperature on the microstructure and properties of AA7050 alloy was investigated.The results show that the alloy AA7050 has obvious aging hardening effect,the higher the pre-aging temperature,the faster the hardening rate.And the alloy shows good over-aging resistance when aged at temperatures not higher than 135 ℃ for 12 h.Guinier-Preston(GP) zones become the main precipitate in grains,and the fine and continuous η equilibrium phase distributes along the grain boundaries when aged at 135 ℃ for 12 h.Meanwhile,no obvious precipitate free zone(PFZ) is observed,and the strength of the alloy is located at sub-peak value.During the higher temperature two-step aging at 170 ℃,the strength of the alloy raises up firstly and then decreases down,and a preferable comprehensive mechanical properties is obtained when aged for 2 h.Here,the dominant strengthening phase in grains is composed of GP zones and metastable η′ phase,the stable and discontinuous η phase along grain boundary,and the PFZ of 10-20 nm in width.With the time prolonging at the second step aging,the strength fall down rapidly owing to that a large number of the metastable η′ phase transforms into the more stable η phase.更多还原