(中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 通過分級(jí)淬火方法獲得7050鋁合金的時(shí)間—溫度—性能(TTP)曲線。結(jié)果表明：合金TTP曲線的鼻尖溫度為330 ℃，淬火敏感溫度區(qū)間為240~420 ℃；等溫保溫時(shí)，過飽和固溶體分解析出第二相粒子，在330 ℃附近，第二相(主要為η平衡相)的析出速率達(dá)到最高；隨著時(shí)間的延長，晶內(nèi)η相數(shù)量增加、尺寸變大，時(shí)效后粒子周圍出現(xiàn)無沉淀析出區(qū)，導(dǎo)致強(qiáng)化效果顯著降低；晶界處η相粒子粗化，由不連續(xù)分布形貌轉(zhuǎn)變?yōu)檫B續(xù)分布形貌，無沉淀析出帶寬化；鼻尖溫度的高相變驅(qū)動(dòng)力和較快的擴(kuò)散速率是η相析出和長大的主要原因，建議在淬火敏感區(qū)間應(yīng)加快淬火冷卻速率避免平衡相的析出，而高于淬火敏感區(qū)間溫度時(shí)可適當(dāng)降低冷卻速率減小熱應(yīng)力的影響。
關(guān)鍵字: 7050鋁合金；TTP曲線；淬火敏感性
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract: The time—temperature—property (TTP) curve of aluminum alloy 7050 was determined by an interrupted quench method. The results show that the quench sensitive temperature range of TTP curve of alloy is 240−420℃ with the nose temperature of 330 ℃. Microstructure observation indicates that the supersaturated solid solution decomposites and particles precipitate during quench process, the precipitation rate is the highest at about 330 ℃. A number of coarse equilibrium η particles precipitate at grain boundaries and in the grains during isothermal-holding at 330 ℃. Prolonging holding time leads to more and coarser η particles in the matrix, which results in loss of solutes and decrease of subsequent aging hardening effect, and more spaced η particles at the grain boundary that widen precipitation free zone. In the quench sensitive sector, primary precipitating reasons of η particles are severe phase transformation driving force and high diffusion rate of solute atoms. According the results, speeding up the cooling rate in the quench sensitive sector to reduce the precipitation of equilibrium phase is meaningful, and at higher temperature, decreasing the cooling rate is helpful to relieve the effect of thermal load.
Key words: 7050 aluminum alloy; TTP curve; quench sensitivity
