拡散接合した異種金属材料の接合強さと超音波因子との関係

抄録

Ferrous (mild steel and stainless steel) and non-ferrous (Ti and Ni) alloy plates were diffusion-welded under thermal cycles including the solid-state transformation temperatures of the mild steel and titanium by placing them in the cylindrical electrodes, and the relation between the shear strength of joints τ_j and the ultrasonic echo intensity from the joint interface was investigated. The relation between the formation of reaction layer at the joint interface and the ultrasonic echo intensity was also investigated. In the mild steel/Ti and stainless steel/Ti joints, a brittle reaction layer was formed at the joint interface, and no relation between τ_j and the area of joints A_j (the area of good welding estimated from the fracture surface) was found. No relation between τ_j and the diameter D_u estimated from the distance of low ultrasonic echo intensity from the joint interface was also found. In the mild steel/Ni joints, no reaction layer was formed at the interface. The strength of the joints varied linearly with the area A_j, and had a quadratic relation with D_u. When no reaction layer was formed at the interface, the echo intensity ratio (R_e) was in good agreement with the reflectivity (r) at the interface over the joined region. When the reaction layer was formed at the interface, the variation of R_e disagreed with that of the calculated echo intensity ratio.