Enhanced interface formation in friction stir welding of dissimilar Ti-Al metals by interlayer design

The interfacial reaction between Ti and Al is a primary cause of the formation of brittle intermetallic compounds. The formation of brittle compounds on Ti-Al interface leads to the significant decrease of properties in friction stir welding of dissimilar Ti-Al metals. To solve this problem, we proposed a molecular dynamics (MD) model based on Embedded Atom Method (EAM) potentials for the optimal selection of interlayers on dissimilar interface of Ti-Al in FSW. In comparison with FSW without Interlayer metals, Ti-Al interfacial diffusion is suppressed by the design of interlayers. Among the interlayers, Cu exhibit the most pronounced suppression effect on Ti-Al interfacial diffusion, achieving 42.36% and 12.48% reduction in diffusion coefficients for Ti and Al atoms respectively, along with a 39.31% decrease in diffusion layer thickness. The systematic study shows that interlayer can enhance the mechanical bonding in FSW of Ti-Al metals. The further experiments show that the yield strength and tensile strength of the Ti-Al welded joints with Cu, Fe, and Mg interlayers were significantly improved compared to those without interlayers. The welded joints with Cu interlayer exhibited the maximum tensile strength, achieving an increase of 31.55%. The welded joints with Mg interlayer achieved the highest yield strength with a 29.20% enhancement.