Effects Of In-situ Al₃Ti On Grain Structure In Friction Stir Welds Of Aluminum Alloy

By adding a groove inside the nugget zone,titanium-aluminum mixed powder can be introduced into friction stir welding(FSW).Intermetallic particles can be produced in situ due to high heat input and severe plastic deformation during FSW.The relationship between the thermal stability of grain structure and the second phase particles in the welds was studied and discussed.The results show that in the weld nugget zone,the more passes being used in the process the more uniform the powder distributed in the welded area and also the reaction would be more severe.Meanwhile by adding the powder into the nugget zone,it would enhance the mechanical property as well.At the same time abnormal grain growth(AGG)region of heat-treated samples decreased significantly with titanium powder addition as compared with that without titanium powder addition.The results further suggest that AGG after heat treatment can be restrained by introducing second phase particles into the nuggets zone.Meanwhile,it is found that with the increase of FSW passes,titanium powders are dispersed more homogeneously and the AGG region deceases,thus the thermal stability of grain structure in weld nugget is improved.