【作者】 李松；

【导师】 陈康华；

【作者基本信息】 中南大学 ， 材料学， 2003， 硕士

【摘要】 通过热处理改善合金化程度较低的中高强可焊Al-Zn-Mg系铝合金的抗应力腐蚀性能并保持合金强度是尚待研究的问题。本文研究了固溶后降温预析出调控7A52和7039合金晶界和晶内析出状态的作用及其对力学性能和抗应力腐蚀性能的影响。 通过热处理后合金显微组织观察，发现固溶后降温预析出可以扩大中高强可焊铝合金晶内和晶界析出状态的差异。降温预析出至400℃以上，可以使预析出仅限于晶界上，而晶内几乎无析出。而在370℃预析出处理将导致晶内和晶界同时析出。 高温预析出对时效硬化和拉伸力学性能有一定影响。控制预析出温度在400℃以上，可以保证7A52和7039合金时效沉淀硬化效果，拉伸强度和硬度基本不变，屈服强度略有提高，延伸率保持在13％。 应力腐蚀开裂和导电率的测试表明：高温预析出处理可明显提高7A52和7039合金不同时效状态下的电导率和抗应力腐蚀性能，预析出温度越低，抗应力腐蚀性能越好：400℃以上的预析出，在保持合金强度的同时，显著改善合金的应力腐蚀抗力。更多还原

【Abstract】 The problem of improving resistance to stress corrosion cracking (SCC) of moderate and high strength weldable Al-Zn-Mg series aluminum alloys with non-deteriorated strength by heat treatment was not still resolved. The effects of the high temperature near-solvus pre-precipitation following after higher temperature solution treatment on matrix and grain groundary (GB) precipitates and mechanical properties and stress corrosion cracking resistance were investigated .Alloys structure after heat treatment indicated that high temperature pre-precipitation after solution could enlarge the difference of precipitates of grain and grain boundary, high temperature pre-precipitation above 400 ℃ could limit pre-precipitation to the GB, yet precipitates hardly existed in the grain. Pre-precipitation treatment at 370℃ incurred pre-precipitates in the grain and GB.High temperature pre-precipitation had a certain influence on age-hardening and tensile properties of 7A52 and 7039 alloys, high temperature pre-precipitation at 400 ℃ could retain ageing precipitation hardening, tensile strength and hardness were invariable basically, yield strength was enhanced slightly, and elongation was 13%.The measurement of electrical conductivity and stress corrosion cracking show that high temperature pre-precipitation could enhance electrical conductivity and resistance to stress corrosion cracking of 7A52 and 7039 alloys at different tempers evidently, and pre-precipitation temperature was lower, resistance to stress corrosion cracking was higher; pre-precipitation treatment above 400 ℃ could improve resistance to stress corrosion cracking obviously with retaining alloys strength.更多还原