Microstructural Modification and High-Temperature Grain Stability of Aluminum in an Aluminum-Titanium Friction Stir Weld with Zinc Interlayer

In dissimilar friction stir welding (FSW), the presence of a third interlayer material can have a positive influence on local ternary chemical reactions due to complex mechanical mixing in the weld nugget. This leads to a reduction and distribution of intermetallic compounds as fine particles in the weld nugget. These fine particles can provide high-temperature grain stability. In the present investigation, a zinc (Zn) interlayer was used during the FSW of aluminum (Al) with titanium (Ti). X-ray computed tomography results revealed the occurrence of mechanical mixing of Zn with both Al and Ti. To understand the nature of the weld nugget at high temperatures, heat treatment of the weld was carried out at 500 degrees C for 60min. The detailed mechanisms leading to the superior grain stability of Al in the weld nugget were investigated. The improvement in grain stability of Al may open up a new area of research and development to produce new materials with high-temperature grain stability.