Influence of welding process parameters on the microstructure and shear strength of TA15/304SS vacuum diffusion welded joints

A study was conducted on the dissimilar metal connection and joint between TA15 titanium alloy and 304 stainless steel. The experimental results show that at welding temperatures of 850-950 ℃, the diffusion zone of the joint (β-Ti) District and (α + β) Ti biphasic region increases with the increase of temperature, element diffusion is more complete, joint pores gradually decrease, and an increasing number of layered products are observed. The layered products are mainly interface layers composed of intermetallic compounds, namely σ-Fe (1st layer), FeTi + Fe₂Ti (2nd layer), FeTi + β-Ti (3rd layer) and β-Ti (4th layer). When the welding temperature is 900 ℃, the welded joint reaches its maximum shear strength of 108MPa. As the welding time increases, the microstructure and composition of the welded joint are similar to those of the welding temperature parameter joint, but the influence of welding time on the shear strength of the joint is relatively small. When the welding time is 80 minutes, the shear strength reaches its maximum value, and the fracture surface exhibits a brittle ductile mixed fracture feature dominated by toughness.