Friction stir welding parameters: a tool for controlling abnormal grain growth during subsequent heat treatment

Recent investigations showed that the fine weld nugget grain structure of friction stir welds (FSW) undergoes abnormal grain growth (AGG) in the post-weld solution heat-treated condition. This significantly deteriorates the strength of FSW of high-strength heat-treatable Al-alloys. In the current research, various welds of AA2095 sheets were prepared by manipulating the FSW parameters, and subsequently heat-treated to investigate the influence of the process parameters (feed rate and tool rotation speed) on the extent of AGG. Characterization of the microstructure and tensile properties revealed that the tool rotational speed and the feed rate appreciably affect the extent of AGG. The higher the rotation speed the lower the AGG at low-to-intermediate feed rates.