Effect of copper interlayer to the microstructure and strength of alumina/304 stainless steel joint brazed with silver‐copper‐titanium filler

Abstract

Alumina and 304 stainless steel were brazed with silver‐copper‐titanium filler+copper foil. The effect of adding copper foil to the filler on the microstructure of the alumina/304 joint was studied, and the reasons for the effect of adding copper foil with different thicknesses on the joint performance were also analyzed. The standard microstructure of alumina/304 joint with silver‐copper‐titanium+copper foil filler is alumina ceramic/copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) continuous layer+copper titanide (TiCu)/silver solid solution+copper solid solution/titanium compound with iron (1 : 2) (TiFe2)+iron‐chromium compound/304 stainless steel. The added copper foil inhibits the diffusion of titanium elements, thereby reducing the formation of the brittle copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) and alleviating the residual stress. In addition, after adding copper foil, the copper solid solution is distributed in blocks in the joint, which also improves the plastic deformation ability of the joint. Under the synergistic effect of these two effects after adding copper foil, the joint strength is improved. When the copper foil was 200 μm, the shear strength is 198.10 MPa.

Effects of Interlayer on the Microstructure and Mechanical Properties of Resistance Spot Welded Titanium/Steel Joints: A Short Review

“…The cross-section morphology of the joint has the following characteristics: Firstly, the base material interface inside the molten core has disappeared, and the molten core that is formed is macroscopically homogeneous. The flowing molten metal is mixed under the action of electromagnetic force and then solidifies to form an approximately homogeneous welded joint [45,46]. Secondly, the welded joint shifts significantly to the titanium side.…”