Molecular dynamics simulation of strengthening dependence on precipitate Cr composition in Fe-15at.%Cr alloy

•This study employ Molecular Dynamics simulation to study the interaction of an edge dislocation with Chromium precipitates.•The precipitate Cr composition was varied in order to investigate the effect on strengthening.•Critical unpinning stress was found to vary with the precipitate Cr composition but not up to what was reported previously.•Analytical models were found to underestimate the results from atomistic simulations.•Additionally, the study confirmed that α’ precipitation results in the hardening of high Cr ferritic/martensitic steels. Molecular Dynamics simulation was employed to study precipitate composition dependence on strengthening. Edge dislocation interaction with pure, 80at.%, and 60at.% Cr precipitates of different sizes in a matrix of Fe-15at.%Cr was investigated. The precipitates were found to be relatively hard. This is evident from the absence of shearing mechanism after the dislocation has bypassed them, the formation of an Orowan-like dislocation shape, and comparatively higher stress values. Precipitates with higher Cr content were found to greatly impede dislocation glide as indicated by the time taken by the dislocation to bypass them. The composition dependence on critical unpinning stress was also observed. The interaction of edge dislocation with precipitates having higher Cr composition leads to higher critical unpinning stress. The extent of critical unpinning stress dependence on precipitate composition is, however, not as high as was reported previously. Besides, the study has also confirmed the fact that α’ precipitation results in the hardening of high Cr ferritic/martensitic steels.