Grain Thermal Instability and Heat Treatment Technology for Aluminum Alloy Welded by FSW

Chuan-hong LUO, Feng-bo DONG, Li-jie GUO, Xiang-fu WEI


The grain thermal instability and heat treatment technology was researched to meet the special requirements of 2219 aluminum alloy plate was obtained by friction stir welding. The microstructures and mechanical properties were investigated correspondingly in order to study the mechanism of abnormal grain growth and put forward the corresponding control measures. The results show that there are no enough precipitation phases existed in the grain boundary of nugget after the friction stir welding, grain is of thermal instability and the grain grows easily, the grain size is up to a millimeter level in the current heat treatment. Through the special recrystallization technology with high temperature oscillating heat treatment to hold the fine grain at short time, the ductility of welded joints can be restored and softening problem of joints can be eliminated, which will improve the performance in mechanical intensity of aerospace aluminum alloy.


Friction stir welding, Microstructure, High temperature oscillation, Thermal instability


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