Microstructure and pitting corrosion of armor grade AA7075 aluminum alloy friction stir weld nugget zone-Effect of post weld heat treatment and addition of boron carbide  

作　　者：P.VIJAYA KUMAR G.MADHUSUDHAN REDDY K.SRINIVASA RAO 

机构地区：[1]Department of Mechanical Engineering,R.I.T. [2]Defence Metallurgical Research Laboratory [3]Department of Metallurgical Engineering,Andhra University

出　　处：《Defence Technology（防务技术）》2015年第2期166-173,共8页Defence Technology

摘　　要：Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding.In recent times FSW is being used for armor grade AA7075 aluminum alloy in defense,aerospace and marine applications where it has to serve in non uniform loading and corrosive environments.Even though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion resistance.The present work involves use of retrogression and reaging(RRA) post weld heat treatment to improve the corrosion resistance of welded joints of aluminum alloys.An attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt position.The effects of peak aged condition(T6),RRA and addition of B4C nano particles on microstructure,hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been studied.Even though RRA improved the pitting corrosion resistance,its hardness was slightly lost.Significant improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.Friction stir welding （FSW） of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion welding. In recent times FSW is being used for armor grade AA7075 aluminum alloy in defense, aerospace and marine appli- cations where it has to serve in non uniform loading and corrosive environments. Even though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion resistance. The present work involves use of retrogression and reaging （RRA） post weld heat treatment to improve the corrosion resistance of welded joints of aluminum alloys. An attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt position. The effects of peak aged condition （T6）, RRA and addition of B4C nano particles on microstructure, hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been studied, Even though RRA improved the pitting corrosion resistance, its hardness was slightly lost. Significant improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.

关 键 词：7075铝合金 搅拌摩擦焊 焊后热处理 碳化硼颗粒 抗点蚀 微观结构 装甲 7075合金 

分 类 号：TG453.9[金属学及工艺—焊接] TG441.8