Abstract:

The effects of accumulative hot rolling followed by solution treatment on the microstructural evolution and fracture behavior of 30CrMo/316L multilayered composites have been investigated. A scanning electron microscope equipped with an electron backscatter diffraction probe, a laser confocal microscope, an electron probe microanalysis, and a universal testing machine were employed to characterize the microstructures and mechanical properties. The results indicate that solution treatment transformed the microstructure of the 30CrMo layer from ferrite to martensite, while the 316L layer remained austenitic but transitioned from the rolled to the recrystallized state. Additionally, solution treatment significantly enhanced the mechanical properties of the composite, leading to an increase in yield strength and ultimate tensile strength to 744 and 1106 MPa, respectively—258 and 276 MPa higher than those of the hot-rolled plate. The enhancement in strength is primarily attributed to the formation of high-strength martensite in the 30CrMo layer. During deformation, the composite interface effectively impeded crack propagation and induced step-like deflection. However, the formation of cross-layer grains facilitated crack nucleation at grain boundaries, leading to rapid crack propagation and instantaneous fracture. Therefore, preventing the formation of cross-layer grains during the heat treatment process is crucial, as their presence weakens the interfacial strengthening effect of the composite plate. This study provides valuable insights for the design and development of multi-layered steels.

Key words: 30CrMo/316L multilayered composite, Accumulative rolling, Solution treatment, Microstructural evolution, Fracture mechanism