Effect of the grain boundary character distribution on the self-organization of adiabatic shear bands in 1Cr18Ni9Ti austenitic stainless steel

The self-organization of adiabatic shear bands (ASBs) in the steel with a different grain boundary character distribution (GBCD) was investigated using the radial collapse of thick-walled cylinders. GBCD of 1Cr18Ni9Ti austenitic stainless steel was optimized by thermo-mechanical treatment. The results showed that the proportion of special grain boundaries, especially the Σ3 grain boundaries, were increased from 27.8, 18.9 to 72.5, 55.8%, respectively. And the high-angle grain boundaries were replaced or interrupted by the low-angle grain boundaries and special grain boundary clusters. The results of optical microscopic examination showed that the shear bands mainly propagated along the clockwise direction, and the multiple shear bands influenced each other along with bifurcation and merging. Also, the number and spacing of the shear bands of the solution treatment specimen (ST specimen) and thermo-mechanical treatment specimen (TMT specimen) were the same, which meant that GBCD optimization had no obvious effect on the nucleation of shear bands. However, the lengths of ASBs in TMT specimen were much shorter than those of the ST specimen under the same deformation conditions. The slower propagation rate of ASBs in TMT specimen suggested that by introducing a large number of special grain boundaries, the GBCD optimization hindered the propagation of ASBs and improved the damage resistance under high-strain-rate loading. Also, voids were nucleated preferentially in the ASBs and coalesced along ASBs, and cracks formed finally.