Eliminating the tearing defect in Ti-6Al-4V alloy joint by back heating assisted friction stir welding

摘要

To eliminate the tearing defect in friction stir welding (FSW) Ti-6Al-4V alloy joint, back heating assisted FSW (BHAFSW) method was put forward in this study. Using different back heating temperatures, joint formation and microstructure were mainly discussed. Results show that the temperature gradient along thickness plays a more important part than the welding peak temperature affecting the tearing defect. With increasing the back heating temperature, size of the tearing defect gradually decreases due to reduced temperature gradient. When using 480 degrees C, defect-free BHAFSW joint with fully lamellar structure along thickness and higher hardness can be obtained. Moreover, the BHAFSW can effectively reduce tool wear during welding.