时效工艺对7A85铝合金力学和晶间腐蚀性能的影响

Effect of ageing processes on mechanical properties and intergranular corrosion of 7A85 aluminum alloy

采用拉伸试验、晶间腐蚀实验、透射电镜观察等方法,研究时效工艺对7A85铝合金显微组织、力学性能和晶间腐蚀行为的影响。结果表明:7A85铝合金的T6态晶内分布着大量细小而弥散的GP区和少量η′相,晶界上析出相(η相)连续分布,无明显的无沉淀析出带(PFZ);T73态晶内析出相尺寸和间距都变大,晶界析出相长大粗化、呈不连续分布,PFZ带宽化,具有良好的抗晶间腐蚀性能,但强度略低;回归再时效处理后的7A85铝合金具有与T6态相似的晶内组织和与T73态相似的晶界组织,合金的抗拉强度及电导率分别为731.7MPa和36.5%(IACS),即合金同时具有较好的强度和抗腐蚀性能。合金的晶间腐蚀敏感性与晶界析出相和无沉淀析出带有关,晶界析出相尺寸越大,分布越不连续,PFZ越宽,合金腐蚀敏感性越小。

The influence of aging process on mechanical properties and intergranular corrosion of 7A85 aluminum alloy wasinvestigated by tensile testing and intergranular corrosion testingcombining with transmission electron microscope. The results show that,a large quantity of GP zones and someη′phasesdisperse in grain, with continuous secondary phases in grain boundary, and the precipitation free zone（PFZ）doesnot exist in the T6 temper.7A85 aluminum obtains a favorable corrosion propertywith the phases inthegrain boundary becomingdiscontinuous and PFZ widening in the T73 temper. 7A85-RRA, which has the T6-like grain-interior and the T73-like grain-boundary morphology, shows good comprehensive performance, withthe combinations of tensile strength of 731.7 MPa and electrical conductivity of 36.5%（IACS）. Corrosion sensibility of alloy is related to the characteristics of equilibrium phase and precipitation free zone at grain boundary, with the equilibrium phases discontinuous and PFZ widening, the corrosion sensibility of alloy decreases.