(1．長沙學(xué)院 機(jī)電工程系，長沙 410003；2．中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用室溫拉伸、抗晶間腐蝕性能測試(IGC)、光學(xué)顯微鏡(OM)及透射電鏡(TEM)觀察等手段，研究3種回歸冷卻速率(17 ℃/s，3 ℃/s，0.02 ℃/s)對回歸再時效(RRA)態(tài)7050鋁合金力學(xué)性能及抗晶間腐蝕性能的影響。結(jié)果表明，在快冷(17 ℃/s)條件下，回歸態(tài)組織的過飽和固溶體含有較高的空位濃度，有利于再時效析出，再時效態(tài)組織的晶界析出相為較粗大的非連續(xù)顆粒，并有較寬的無沉淀析出帶(PFZ)；慢冷(3 ℃/s或0.02 ℃/s)條件下，在冷卻過程中晶界和晶內(nèi)均析出了微小的第二相，導(dǎo)致固溶體內(nèi)空位濃度降低，影響再時效析出，使得再時效態(tài)組織的晶界析出相顆粒粗細(xì)不均勻，無沉淀析出帶變窄。相應(yīng)地，隨冷卻速率降低，合金的拉伸強(qiáng)度單調(diào)下降，抗晶間腐蝕性能先下降，后略有升高。
關(guān)鍵字: 7050鋁合金；回歸再時效(RRA)處理；回歸冷卻速率；力學(xué)性能；晶間腐蝕
（1. Department of Mechanical and Electrical Engineering, Changsha University, Changsha 410003, China;2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of retrogression cooling rate (17 ℃/s, 3 ℃/s and 0.02 ℃/s) on the mechanical properties and resistance to intergranular corrosion of 7050 aluminum alloy were investigated by tensile testing, intergranular corrosion (IGC) testing, optical microscopy(OM) and transmission electron microscopy(TEM). The results show that by quenching at the rate of 17 ℃/s (quick cooling), the supersaturated solid solution as retrogression contains high vacancy concentration which is beneficial to re-aging. So, there are wider precipitate free zones (PFZ) and coarser discontinuous precipitates at grain boundaries in the re-aging microstructure. However, slow cooling at the rates of 3 ℃/s and 0.02 ℃/s, some of fine particles of the second phase precipitate gradually on grain boundaries and in grains, which leads to decreasing the vacancy concentration generally. Precipitation is difficult during re-aging, and the precipitate size at the boundary is not uniform besides ambiguous precipitation free zones (PFZs). Accordingly, with the decrease of the cooling rate, the tensile strength decreases monotonously, but the resistance to corrosion decreases firstly and then increases slightly.
Key words: 7050 aluminum alloy; retrogression and re-aging (RRA) treatment; retrogression cooling rate; mechanical properties; intergranular corrosion
