Effect of dislocation network on precipitate morphology and deformation behaviour in maraging steels: Modelling and experimental validation

In maraging steels subjected to High Pressure Torsion (HPT), overaging (OA) leads to considerable reduction in ductility as compared to the overaged counterparts in the as-received (AR), hot-rolled state. Atom probe tomography has revealed a corresponding difference in morphology of Fe2Mo precipitates between the HPT+OA and the AR+OA conditions, the former being flat, disc shaped, while the latter are spherical. In order to reveal the role of the high dislocation density introduced during HPT on this change of precipitate morphology and consequent mechanical behaviour, phase field modelling study was carried out. It is shown that the increased solute mobility pathway provided by dislocations through pipe diffusion leads to the evolution of this new precipitate morphology in the otherwise slow diffusing species-Mo. Using a micromechanical finite element model, we correlate the changes in morphology to the differences in ductility in the overaged AR and HPT processed samples. [Display omitted]