financially supported by the National Natural Science Foundation of China(Grant Nos.51204108 and 51675337);the National Research Foundation for Doctoral Program of Higher Education of China(Grant No.20120073120120);the Shanghai Committee of Science and Technology(Grant No.11ZR1418100).
Abnormal grain growth(AGG)has been widely observed in many friction stir welded(FSWed)joints during post-weld heat treatment(PWHT).The coarse grain structure not only reduces the strength of the joint but also limits ...