Cerium-alloyed ultra-high strength maraging steel with good ductility: Experiments, first-principles calculations and phase-field simulations

Abstract

Improving ductility while achieving ultra-high strength has always been a challenge in developing of high performance maraging steels. To this end, the study of the influence of Ce on the mechanical performance of B2–NiAl precipitation strengthened maraging steel was performed via experimental characterization combined with first-principles calculations-based phase-field simulations and crystal plasticity simulations. The tensile test revealed that the Ce-bearing maraging steel possesses a remarkable combination of ultimate tensile strength of ∼2000 MPa and tensile ductility of ∼10%. The microstructures at various scales were characterized by EBSD, HRTEM and APT. It was found that Ce exhibits a notable effect on the precipitation behavior of B2–NiAl particles because the presence of Ce decreases the precipitation driving force of B2–NiAl phase. EBSD characterization revealed that Ce-bearing steel possesses a higher fraction of HAGBs which facilitates the improvement the ductility of the experimental steel. Reconstruction of parent austenite grains and analysis of martensite variants selection were performed, and the results indicated that the lowering of the Ms temperature of the steel caused by Ce leads to more length fractions of V1/V2 and V1/V5 inter-variant boundaries, which contribute to the formation of higher fraction of HAGBs.