Investigation of interface microstructure and mechanical properties of Kovar alloy/304 stainless steel composites fabricated by explosive welding

The integration of 4J29 Kovar alloy (Fe-29Ni-17Co) and stainless steel can reduce material costs while meeting functional performance requirements in applications such as electronic packaging. In this study, a Kovar alloy/304 stainless steel (4J29/304) composite plate was fabricated via explosive welding, and its microstructure and mechanical properties were investigated. An oblique collision welding model was established by smoothed particles hydrodynamics (SPH) algorithm, which reproduced the interface evolution and physical phenomena during plates collision. The results show that the interface between the two materials exhibits a sinusoidal waveform, accompanied by vortices distributed on both sides of individual waves. Equiaxed grains formed through dynamic recrystallization are observed along the deformed regions adjacent to the interface, while the vortex regions consist of columnar grains and fine equiaxed grains resulting from jet-induced rapid solidification. The microhardness of the flyer plate (4J29) and base plate (304) reach a maximum value near the interface, increasing by 35.3% and 81.9%, respectively, relative to their respective base materials. The shear strength of the 4J29/304 composite exceeds 360 MPa, with shear failure occurring within the 4J29 matrix, indicating excellent interfacial bonding quality.