Deformation and Fracture Behaviour of Heterostructure Mn8/SS400 Bimetal Composite

This study examines the deformation behaviour and fracture mechanisms of bimetal composites (BCs) composed of high-carbon medium-manganese steel (Mn8) and low-carbon steel (SS400), fabricated through hot roll bonding. The research highlights the effect of varying thickness ratios on the mechanical properties of Mn8/SS400 BCs. The microstructure and interfacial characteristics were analysed using scanning electron microscopy (SEM), revealing a well-bonded and defect-free interface with distinct elemental distributions. Tensile and bending tests were conducted to evaluate the composites' mechanical performance, highlighting the synergistic effects of Mn8's high strain hardening capacity and SS400's ductility. Mathematical models, including the rule of mixtures (ROM) and the long-wavelength approach (LWA), were employed to predict the tensile strength and plastic instability strain (PIS), with experimental results showing deviations due to interfacial strengthening mechanisms and dislocation pile-ups. The findings provide insights into the interplay between layer thickness ratios, interfacial properties, and strain hardening, offering valuable guidance for optimising the design and industrial-scale production of Mn8/SS400 BCs.