Effect of Nb element on onset of deformation-induced martensitic transformation in iron: Insight from molecular dynamics simulations

H Sun and JF Jin and WY Liang and SJ Li and C Chen and MT Wang and GW Qin, COMPUTATIONAL MATERIALS SCIENCE, 253, 113892 (2025).

DOI: 10.1016/j.commatsci.2025.113892

Niobium (Nb) is a crucial alloying element in advanced steels, influencing deformation-induced martensitic transformation (DIMT) in advanced high-strength multiphase steels. In this work, molecular dynamics (MD) simulations were used to investigate the effects of Nb on DIMT characteristics in iron, focusing on the onset strain (epsilon S), final strain (epsilon F) and complete transformation rate (eta C) of DIMT at atomic level. MD simulations reveal that Nb stabilizes residual face-centered cubic (FCC) austenite at 300 K, maintaining approximately 56 vol% austenite with Nb concentrations between 0.05 and 0.4 at.%. Tensile simulations at 300 K for these Nb concentrations show the yield stresses ranging from 7.55GPa to 8.94GPa, attributed to a combination of phase transformation and dislocation mechanisms. Across these Nb concentrations, the epsilon S remains consistent at approximately 4.34 %, and the eta C is about 98 %. The formation of Lomer-Cottrell (LC) dislocations during yielding acts as a precursor for DIMT. Varying Nb content alters the competition between interface-and LC-triggered DIMT mechanisms. These findings provide valuable insights into the role of Nb in controlling DIMT and offer theoretical guidance for designing and developing high-performance Nb-alloyed steels.

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