The influence of pin geometry on bonding and mechanical properties in friction stir weld 2014 Al alloy

Friction stir tool is the key art of friction stir welding process. The influence of the welding structure and the mechanical properties has been investigated. For this purpose, four different stir pins, two of them are column pin and taper pin and the other two are the same size but with screw thread, were used to carry out a welding process. Microscopic examination of the weld zone and the mechanical property tests results showed that the best bonding was obtained with screw pitched taper stir pin. The appearance of the weld is well and no obvious defect is found using this tool. The grain of the weld nugget is very fine and the precipitation distributes equably. This study will be benefit to direct the friction stir tool design.