Influences of tool pin profile on microstructure , mechanical and defects of Friction stir welded 7075 aluminum alloy

In this study, effect of geometry of the pin profile on microstructure, mechanical and defects of FSWed 7075 alloy was investigated. Three pins with cylindrical, square and triangle geometry were used for welding. Microstructure of the welding zone showed that the tunnel hole produced by triangle pin has smaller dimensions compared to cylindrical pin. On the other hand, results of optical microscope indicated that the size of grains resulted from square pin is smaller than the other kinds of tools. Also, the results showed that when the pin is cylindrical, tunnel, kissing bond, and zigzag line defects are formed. On the other hand, when the pin is triangle, original joint line with severe plastic deformation and crack defects are created. After welding with the square pin, tensile strength and the hardness were acquired 490 MPa and 160 HV respectively that were the maximum values compared to other pins

Keywords:

7075 Al alloy , Friction stir welding , Pin profiles , Microstructure , Mechanical properties