【作者】 刘娜；

【导师】 张静武；

【作者基本信息】 燕山大学 ， 材料学， 2010， 硕士

【摘要】 本文研究了7075铝合金不同时效条件下的硬度和组织特征。对7075铝合金进行了压应力时效和常压下的T6时效、双级时效,对时效后的合金进行了硬度分析和TEM组织分析,依据溶质晶界非平衡偏聚理论探讨了应力时效机制。结果表明:7075铝合金常压T6时效处理后的硬度高于双级时效,晶内析出η’相,尺寸细小,分布均匀,晶界析出相连续分布;合金经DA时效(双级时效)处理后,析出相尺寸略有增大,出现了一定宽度的晶界无析出带。合金在0.3σs压应力下经不同时间时效,硬度相差不大。在不同弹性应力下时效一个小时,各试样硬度结果不同,其中当应力为0.5σs时,硬度值最大,其组织特征较好,所有试样组织均没有出现晶界无沉淀带。在弹性应力场中的120℃×60 min时效,其硬度高于T6处理。组织观察表明应力时效消除了PFZ,抑制了晶界析出相,是溶质在压应力下发生晶界非平衡偏聚所致。更多还原

【Abstract】 The hardness and microstructure characteristics of 7075 aluminum alloy was studied under different aging condition.Compressive stress aging, T6 aging and double aging was carried out to 7075 aluminum alloy. After that samples were researched with hardness test and transmission electron microscope and the stress aging mechanism was studied according to the solutes non-equilibrium grain boundary segregation theory. The results showed that:The hardness of samples after T6 aging was higher than that of double aging.Dispersedη’ phase precipitated in the matrix with small size, grain boundary precipitates distributed continuously. After double aging, the size of precipitated phase grow bigger with PFZs of certain size.The hardness values of samples aged under 0.3σs compressive stress for different time were of little difference. Hardness values of samples aged at different compressive stress for 1 hour were varied. The sample possed the maxium hardness value and the preferable microstructure characteristics when the stress was 0.5σs. PFZs are not found in all the samples.The hardness value of sample aged for 60 min of 120℃under elastic stress fields was higher than that of T6 aging treatment. TEM microstructure showed that stress aging eliminate PFZ and inhibited GBP which was due to the non-equilibrium grain boundary segregation of solutes.更多还原