The evolution of adiabatic shear band in high Co–Ni steel during high strain-rate compression

The microstructural evolution and formation mechanism of adiabatic shear band (ASB) in M54 steel were investigated using split Hopkinson pressure bar (SHPB). Specially, the strain response to ASB was analyzed systematically by strain controlling dynamic compression tests at high strain-rates. The results demonstrated that the ASBs started to form at 23% strain and shearing failure strain was increased to 28% at strain-rate of 4000 s−1. The ASBs in the M54 steel was consist of a transformed adiabatic shear bands (T-ASB) and deformed adiabatic shear bands (D-ASB). The evolution of the ASBs was revealed and the generation of fine equiaxed nano-grains within ASBs was attributed to the rotational dynamic recrystallization mechanism. The twinning process was actually the reverse transformation of ω→bcc and the driving force was the lattice instability of martensite matrix caused by carbon redistribution.