Role of retained austenite on adiabatic shear band formation during high strain rate loading in high-strength bainitic steels

Adiabatic shear band (ASB) is a well-known structure formed during high strain-rate deformation in various metallic materials, and significantly affects dynamic properties as well as ballistic performance. Retained austenite contained in recently developed high-strength martensitic or bainitic armor steels usually triggers a TRansformation-Induced Plasticity (TRIP), which enhances a strain hardening capability. However, this TRIP effect on ASB formation has hardly been investigated yet. In this study, a laboratory-scale split Hopkinson pressure bar was utilized to describe the ASB formation behavior in four high-strength martensitic or bainitic armor steels. Their formation possibilities were then correlated with hardness, strength, and dynamic compressive properties coupled with the TRIP. This TRIP occurring under adequate austenite stability improved the strain hardening, sufficiently absorbed the dynamically applied energy, and effectively suppressed the ASB formation. These behaviors suggest the favorable utilization of retained austenite in high-strength armor steels for wide-range ballistic applications.