Effect of Strain on Microstructure Evolution of 1Cr18Ni9Ti Stainless Steel During Adiabatic Shearing

Dynamic shear test was conducted on the hat-shaped specimen of the thermo-mechanical-processed 1Cr18Ni9Ti stainless steel by using the split Hopkinson pressure bar at ambient temperature. The effect of the shear strain on the microstructure evolution was investigated during adiabatic shearing. The results revealed that the development of adiabatic shear localization went through three stages, including the incubation period, the development stage, and the maturity period. TEM observations showed that the grains in the shear region were elongated, and the elongated grains were gradually evolved into equiaxed nano-grains of 100 nm as shear strain increased. The rotational dynamic recrystallization kinetics calculation showed that subgrains had sufficient time to generate an equiaxed microcrystalline structure by rotation within the deformation time. Based on the observation of the evolution of dislocations and sub-grains in the adiabatic shear region, a model of the microstructure evolution was established during the adiabatic shearing.