Mechanistic study on the influence of semi-solid processing on the interfacial bonding performance of copper-steel bimetallic composites

Abstract

Copper-steel bimetallic composites combine the high thermal and electrical conductivity of copper with the strength and wear resistance of steel, yet their performance and service life remain constrained by interfacial bonding quality. Although semi-solid processing offers a promising route to interface optimization, its mechanistic role in diffusion-assisted bonding remains unclear. Here, molecular dynamics simulations were integrated with experiments to elucidate the effects of semi-solid treatment on the interfacial bonding behavior of ZCuSn10/1045 copper-steel bimetals. Semi-solid treatment induced dendrite fragmentation and recrystallization in the copper alloy, generating near-spherical equiaxed grains enveloped by an Sn-rich liquid phase and promoting Sn segregation at grain boundaries. Among the remelted, semi-solid-treated, cast, and semi-solid + cast samples, the semi-solid + cast sample exhibited the most pronounced interdiffusion of Cu, Fe, and Sn, together with a thicker interfacial diffusion layer and a more continuous metallurgical bonding zone. Specifically, the total diffusion-layer thickness increased from 3.44 to 4.93 μm. Simulations further showed accelerated atomic diffusion and stronger interfacial cohesion, consistent with the increase in average shear strength from 258.1–272.5 MPa. These findings establish a direct process-microstructure-property relationship for interface optimization in copper-steel bimetallic composites.