(1. 湖南科技大學材料科學與工程學院，湘潭411201；
2. 西北工業(yè)大學材料學院，西安 710072；
3.北京航空材料研究院，北京 100095)
摘 要: 利用萬能材料試驗機、透射電子顯微鏡(TEM)和掃描電子顯微鏡(SEM)，研究了熱暴露對7475-T761鋁合金微觀組織和力學性能的影響。結果表明：在100℃熱暴露時，合金強度隨著時間延長略有升高；在125℃熱暴露時，合金強度隨著時間延長略有降低，且力學性能在較長時間內保持穩(wěn)定；當熱暴露溫度高于150℃時，合金強度隨著時間延長急劇降低，伸長率快速升高。其主要原因是基體析出相(MPt)η′和η長大粗化、晶界析出相(GBP)η粗化以及晶界無析出帶(PFZ)寬化。隨著熱暴露溫度升高和時間延長，合金的斷裂機制呈現(xiàn)由沿晶斷裂和韌窩斷裂組成的混合斷裂轉變?yōu)榇┚ыg窩斷裂。影響合金斷裂行為的主要因素是基體與晶界之間的強度差異。
關鍵字: 7475鋁合金；熱暴露；微觀組織；力學性能
（1. School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
2. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an710072, China;
3. Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract:The effects of the thermal exposure on microstructure and mechanical properties of 7475-T761 Al alloy were studied by universal material testing machine, transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results show that the strength of the alloy increases slightly when the alloy is exposed at 100℃. When the alloy is exposed at 125℃, the strength of the alloy decreases slightly and the mechanical properties remain stable for a long time. When the thermal exposure temperature is higher than 150℃, the alloy strength reduces sharply and the elongation increases rapidly with the prolongation of time.Coarsening of matrix precipitates(MPt), coarsening of grain boundary precipitates(GBP), and widening of precipitate free zones(PFZ) should be responsible for the strength decline and elongation rise of 7475-T761 Al alloy during thermal exposure.With increasing the temperature or prolonging the time, the fracture mechanism of the alloy gradually transforms frommixed fracture including intergranular fracture and dimple fracture to transgranular dimple fracture. The main factor that affect the fracture behavior of the alloy is the intensity difference between matrix and grain boundary.
Key words: 7475 Al alloy; thermal exposure; microstructure; mechanical property
