Preliminary Investigation of the Effect of Temperature Control in Friction Stir Welding

Friction stir welding (FSW) is an advantageous solid-state joining process, suitable for many hard to weld materials in the energy, aerospace, naval, and automotive industries. Precipitation strengthened alloys, specifically 2XXX and 7XXX series aluminum alloys, are often joined by FSW to protect the strength of the materials and to avoid cracking. To maximize the strength of FSW joints in these precipitation hardened alloys, the thermal input affect must be better understood. The authors hypothesised that controlling the welding temperature under the dissolution temperature would result in stronger joints. To test the main hypothesis single alloy friction stir “butt” welds were produced, from aluminum 2024-T351 and 7075-T651 alloys, and tensile tested. Spindle speed proportional–integral–derivative (PID) temperature control was implemented to achieve sub-dissolution welding temperatures. This preliminary study will supply additional research to better understand the resulting microstructure, weld properties of sub-dissolution FSW. In addition, a numerical simulation to represent the temperature distribution will be built. Then optimized FSW temperatures could be predicted and tested in these alloys.