Effect of gap on FSW joint formation and development of friction powder processing

Abstract

A gap between two materials is a critical problem for friction stir welding (FSW). It is generated by a mismatch at the interface between two materials and causes defects and porosities due to the lack of material in the joint. In this study, friction powder processing (FPP) is proposed to solve this problem. Metal powder is first added to the gap between and then the FSW is performed. The effect of the gap width on the joint properties was first investigated, and the FPP feasibility was then assessed by adding pure Al powder to the gap between A1050-H24 plates. In addition, the mechanical properties and microstructures were investigated when adding a dissimilar powder, such as Cu powder, to the gap between Al plates. When using pure Al powder, the formation of defects is prevented. When using pure Cu powder, Al₂Cu precipitates were formed in the stir zone, and consequently, the hardness significantly increased.