Microstructures and mechanical properties of A356/2024 bimetals fabricated by solid-liquid roll bonding

Abstract

The present study investigates the process of solid-liquid roll bonding to fabricate A356/2024 Al alloy bimetals. The microstructure, elemental distribution, crystalline structure, hardness, and shear strength near the A356/2024 interface are systematically evaluated. The results demonstrate that cracks, pores, and other defects at the A356/2024 interface gradually disappear as the liquid pouring temperatures and the solid preheating temperatures are increased. At low liquid pouring temperatures or solid preheating temperatures, alloying elements at the interface form hard brittle phases such as Al2CuMg and CuAl2 intermetallics, resulting in high hardness values and reduced bonding strength at the interface. At high pouring temperatures or preheating temperatures, the alloying elements diffuse across the interface, and form a transition zone. The hardness increases gradually in the transition zone, which reduces the interfacial stress, and enhances the bonding strength of the interface. The interfacial shear strength progressively increases with increasing pouring temperatures, and attains a maximum value of 48.4 MPa at a relatively high pouring temperature of 720 °C in the absence of preheating. With preheating at 500 °C, the interfacial shear strength attains a maximum value of 57.93 MPa under the optimum process parameters including a relatively low pouring temperature of 680 °C.