Precipitation kinetics and mechanical properties of nanostructured steels with Mo additions

Abstract

IMPACT STATEMENT The precipitation mechanisms and thermostability of nanoscale precipitates in nanostructured steels are strongly dependent on the diffusion coefficient of elements, which can be effectively tuned by alloying with Mo additions. It is known that nanoscale precipitates strongly affect the precipitation hardening of structural materials. In this study, we report the precipitation kinetics and thermostability of Cu-rich and NiAl nanoprecipitates in nanostructured steels with Mo additions. Atom probe tomography and first-principles calculations revealed that the addition of Mo effectively decreased the diffusion coefficients of Cu, Ni and Al atoms, leading to the change in the precipitation mechanisms from NiAl prior-precipitation with an instantaneous-nucleation mechanism to the Cu prior-precipitation with a continuous-nucleation mechanism. The decreased diffusion coefficient significantly improves the thermostability of nanoprecipitates and strongly enhances the strength of the nanostructured steels.