The aerospace industry is showing increasing interest in the application of friction stir welding (FSW) for joining titanium alloys. FSW of titanium is challenging, especially with conventional tool designs which can result in root defects due to the materials poor thermal conductivity. Recent developments at TWI have led to some excellent results particularly in the areas of process control and stability. In particular, the development of the stationary shoulder friction stir welding technique (SSFSW) which has had a profound effect on weld quality and ease of production.
During SSFSW, a tool probe rotates through a non-rotating shoulder which enables the process to generate a consistent linear heat input throughout the weld cross-section.
TWI has successfully used the SSFSW technique for joining 20mm thickness Ti-6Al-4V alloy sheets.
The process produces an excellent weld surface appearance and a weld strength matching that of the parent material.