Ductile fracture and microstructure of a bearing steel in hot tension

Ductile fracture, such as micro-cavities and micro-voids, inevitably exist and evolve under tensile stress state in metal forming. Ductile fracture sways the mechanical performance of 52100 bearing steel. It is necessary to investigate the influences of strain rate and deformation temperature on both ductile fracture and microstructure evolution. Uniaxial hot tension tests were performed, in which specimens were stretched to failure in the temperatures range from 950 C to 1160 C and in the strain rates range from 0.01 /s to 1.0 /s. Specimens metallographies have been explored after hot tension. Experimental results show that the peak stress decreases when deformation temperature increases and strain rate decreases. The critical strain of stress–strain relationships increases when strain rate increases. Fracture morphology is severe at higher deformation temperatures and lower strain rates. Hot tension deformation capacity is worst at 1160 C and a strain rate of 0.01 /s, has been caused by a larger and coarser grain structure