Rolling in-situ generation of metallurgical and mechanical bonding improves mechanical properties and synergistic deformation ability of semi-solid cast-rolled aluminum/steel composite plate

Abstract

A nowel processing technology was developed to solve the problem of low bonding strength caused by intermetallic compounds (IMCs) of aluminum/steel composites. This approach utilizes semi-solid cast-rolling to fabricate composite plates with a thin metallurgical bonding layer, followed by in situ formation of metallurgical and mechanical bonding through rolling, thereby enhancing the mechanical properties of aluminum/steel composite plate. Results demonstrated that a primary metallurgical bonding layer of approximately 6 μm formed after semi-solid cast-rolling, with a shear strength of only 38.8 MPa, while a reduction rate of 20 % increased the mechanical bonding strength to 46.0 MPa. The optimal mean mechanical bonding strength of 59.5 MPa was achieved at a reduction rate of 30 % with five rolling passes, exceeding the lower limit of the critical reduction rate required for aluminum/steel composite plate preparation by traditional rolling. With an increasing reduction rate, steel deformation, crack gaps (equivalent deformation) in IMCs, and coordinated deformation in composite plates also increase, promoting the formation of secondary bonding with alternating soft and hard phases. At a 50 % reduction rate, the shear strength of the aluminum/steel composite plate reaches 119.0 MPa, representing a 206.7 % increase compared to semi-solid cast-rolling. The ultimate tensile strength (UTS) of the composite plates with a 50 % reduction rate exceeded that predicted by the rule of mixtures by 17.1 MPa, while uniform elongation (UE) and fracture elongation (FE) increased by 35.3 % and 120.0 %, respectively, compared to high-elongation steel. The current study presents a novel investigation into the influence of bonding modes on the shear strength of aluminum/steel composite plates, offering new perspectives for designing and manufacturing dissimilar alloy interfaces.