Establish the strengthening mechanism of the Ag-interlayered joint

Characterize the interfacial reaction layer in cross-section and determine the specific mechanism responsible for the higher nominal strength of Ag-interlayered Al/Cu resistance spot-welded joints.

Background

The study reports that introducing a silver interlayer increases the mean nominal strength of the resistance spot-welded Al/Cu joint from 47.9 MPa to 67.4 MPa and associates this improvement with reduced direct Al–Cu interaction and formation of an Al-rich FCC Al–Ag fusion zone. However, the interfacial reaction layer was not characterized in cross-section, so the observed strength increase cannot be assigned to a specific interfacial metallurgical or fracture mechanism. Resolving this issue requires direct characterization of the reaction layer and its relationship to fracture and joint strength.