Effect of welding parameters and B4C contents on the microstructure and mechanical properties of friction stir welded B4C/6061Al joints

Annealed 2.8 mm thick B4C/6061Al composite sheets with various B4C particle contents (15, 20, 25, 30 wt%) were friction stir welded (FSW) at a tool rotation rate of 1000 rpm and traverse speeds of 50 and 150 mm/min using a single simple-shaped wear-resistant cermet tool. Sound FSW joints were obtained without severe abrasion of the tool. FSW resulted in obvious homogenization and fragmentation of B4C and the re-distribution of the interfacial products, thereby remarkably increased the hardness of the nugget zone. The hardness profiles of the welded joints were hardly influenced by B4C contents but significantly by the welding speeds. “S” line and a B4C depleted region were formed at the top and the bottom of the nugget zone, respectively. However, they did not deteriorate the mechanical properties of the joints. The tensile strength of all the joints was close or even up to that of the base material with the fracture occurring at the base material.