Microstructure and mechanical properties of SUS304/Q235 multilayer steels fabricated by roll bonding and annealing

摘要

The microstructure and mechanical properties of roll bonded and annealed SUS304/Q235 multilayer steels were investigated by using optical microscope (OM), scanning electron microscope (SEM), electron probe micro-analysis (EPMA), electron backscattered diffraction (EBSD), Transmission electron microscope (TEM) and universal testing in detail. Hot rolling with high reduction ratio could strengthen the clad interface due to the interface oxides rupture, increased residual compression stress and sufficient alloy element diffusion. The hardness and tensile strength are increased, while the fracture elongation is decreased sharply with the increasing cold rolling reduction ratio. The hardened SUS304 layers are easy to strain softening, leading to localized necking, wave-like clad interface and nonuniform layer thickness during the cold rolling process. The annealed grain orientations in the separated SUS304 layers also reveal that the overall grain boundaries are across the Q235 layer, which is attributed to the grain coarsening across clad interface during the annealing process. At the grain boundaries in the SUS304 layer, the austenite-to-ferrite transition reveals the serious grain boundary diffusion behavior. Moreover, tensile fracture characteristics reveal that interface delamination cracks are inhibited by annealing treatment, which may be attributed to the sufficient alloy element diffusion at the clad interface.