(中南大學 材料科學與工程學院，長沙 410083)
摘 要: 采用光學顯微鏡、掃描電鏡、透射電鏡、常溫拉伸及斷裂韌性實驗研究回歸溫度及回歸時間對7050鋁合金力學性能和斷裂韌性的影響。結(jié)果表明：回歸過程中，一部分GP區(qū)回溶進入基體，另一部分長大轉(zhuǎn)變?yōu)棣恰湎啵瑫rη′相轉(zhuǎn)變?yōu)棣窍啵窍鄤t不斷粗化。隨著回歸時間的延長，合金的強度先下降至一谷值然后上升至一峰值再單調(diào)下降；再時效態(tài)合金強度先增大后減小，再時效態(tài)合金強度大于對應回歸態(tài)合金強度。在190 ℃回歸時，回歸及再時效7050合金(RRA)的斷裂韌性均隨回歸時間的延長而不斷增大；然而，在170和150 ℃回歸時，回歸及再時效7050合金的斷裂韌性先增大至一峰值然后下降至一谷值再增大。回歸態(tài)合金的斷裂韌性大于對應再時效態(tài)合金的斷裂韌性。隨著回歸時間的延長，合金的斷裂模式由沿晶斷裂向穿晶韌窩斷裂過渡。
關鍵字: 7050鋁合金；回歸再時效；拉伸性能；斷裂韌性
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of retrogression and reaging (RRA) on the tensile property and fracture toughness of aluminum alloy 7050 were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile and toughness tests. The results show that during the retrogression treating, one part of GP zone dissolves into Al matrix and the other grows, and then transforms into η′ phase. At the same time, the η′ phase transforms into η phase constantly. And the η phase becomes coarse gradually. With the retrogression time elongating, the strength of the alloy falls to a valley value before increasing to a peak value, and then monotonically decreases. Meanwhile, the strength of the reaged alloys first increases and then decreases. The strength of the reaged alloys is larger than that of the retrogressed alloys. With the retrogression time elongating, the fracture toughness of alloy 7050 RRA retrogressed at 190 ℃ increases. However, the fracture toughness of alloy 7050 RRA retrogressed at 170 ℃ and 150 ℃ increases to a peak value before decreasing to a valley value and then increases. The fracture toughness of the retrogressed alloys is larger than that of the reaged alloys. With the retrogression time elongating, the main fracture mechanism changes from the intergranular fracture to transgranular fracture.
Key words: aluminum alloy 7050; retrogression and reaging; tensile property; fracture toughness
