Exploring the Interfacial Microstructure Evolution and Bonding Properties of Al/Steel Composite Plates Fabricated Through Semi-Solid Cast-Rolling

This study prepared Al/steel composite plates with high shear strength using semi-solid cast-rolling (SSCR). The results indicate that the semi-solid diffusion effectively reduced the diffusion and reaction rate between Al and steel, thereby impeding the formation of the free FeAl3 phase and mitigating the rapid growth of the Fe2Al5 phase, facilitating the regulation of the microstructure and bonding property. Notably, the morphology of the FeAl3 phase transformed from a loose sponge-like eutectic structure to a densely serrated-like configuration with the increase in the holding time, correlating with an enhancement in shear strength. At a holding time of 120 s, the shear strength of a 5.5 mm thick composite plate reached a notable 68.5 MPa. After a holding time of 120 s, the thickness of the FeAl3 phase stabilized at approximately 9.5 μm. However, the grain size and thickness of the Fe2Al5 phase continued to increase, leading to a subsequent decline in shear strength. Furthermore, shear strength increased substantially with the decreasing thickness of the composite plate. SSCR enabled the formation of dense intermetallic compounds (IMCs) with grain sizes below 3 μm at the Al/steel interface while retaining residual compressive stress within the matrix, yielding shear strength higher than that of composite casting and comparable to composite rolling.