通過(guò)疲勞裂紋擴(kuò)展速率試驗(yàn)和掃描電鏡觀察研究了T7951二次時(shí)效對(duì)室溫空氣環(huán)境下7055鋁合金疲勞裂紋擴(kuò)展行為的影響。結(jié)果表明: 經(jīng)二次時(shí)效處理后, 該鋁合金的裂紋擴(kuò)展速率有所降低; 二次時(shí)效前后鋁合金疲勞斷口的裂紋穩(wěn)定擴(kuò)展區(qū)均為準(zhǔn)解理斷裂, 且均出現(xiàn)平行的疲勞條紋; 二次時(shí)效前鋁合金出現(xiàn)二次裂紋, 其疲勞條紋間距大于二次時(shí)效后的; 二次時(shí)效前后鋁合金疲勞斷口的瞬斷區(qū)均為韌窩型穿晶斷裂。
The effects of secondary ageing of T7951 on fatigue crack propagation behavior of 7055 aluminum alloy at room temperature in the air were investigated through the crack propagation rate test and SEM observation. Results show that the fatigue crack propagation rate of the alloy decreased after secondary ageing. The stable crack propagation areas in fatigue fracture of the aluminum alloy before and after secondary ageing all exhibited quasi-cleavage fracture, and parallel fatigue striations were observed in the above areas. Secondard cracks occured in the aluminum alloy before secondary ageing, and the distance between fatigue striations before secondary ageing was bigger than that after secondary ageing. Transgranular dimple fracture were observed in the final fracture areas in fatigue fracture of the aluminum alloy before and after secondary ageing.