High–strain–rate deformation of a nanoprecipitate–strengthened dual–phase steel

Abstract

High–strain–rate deformation of steels is prone to generating localized adiabatic shear bands (ASB) due to strain localization, leading to plastic instability and fracture. Nanoprecipitate–strengthened austenite–martensite dual–phase (DP) steel is a kind of promising impact–resistant materials due to their high strength and excellent plasticity. In this study, the effects of a combination of nanoprecipitates and the frame structure of DP steels with the hard martensite as the support framework on the dynamic mechanical properties were systematically investigated. The nanoprecipitate–strengthened DP steel exhibited excellent dynamic performance. At a strain rate of 3800 s−1, the maximum flow stress of the DP steel with nanoprecipitates reached ∼ 4067 MPa, which was 1146 MPa higher than its counterpart without nanoprecipitates. High–strain–rate deformation induced the transformation of Cu–rich nanoprecipitates from body–centered cubic (B2) to 9R twin structure, alleviating the stress concentration. Upon high–strain–rate deformation, the high strength of nanoprecipitate–strengthened DP steel induced the formation of a narrow shear band with sever–deformed microstructure. The frame–structure of DP steel restrained the transformation of deformed shear bands (DSB) to transformed shear bands (TSB) due to the deformation–induced martensitic transformation of austenite, delaying the crack formation and propagation.