"Composition Effects on the Mesoscale Plasticity of BCC Alloys" 

Manikandan Muruganandam, MSE PhD Candidate 

Advisor: Professor Anter El-Azab

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ABSTRACT

Reduced activation ferritic steels are promising candidates for structural applications in both nuclear fission and fusion reactors. To understand the mechanical behavior of these steels under irradiation, methods such as dislocation dynamics can be used. Here, we apply dislocation dynamics simulations (DDD) to investigate the yielding behavior of Fe-Cr as model ferritic alloys. In particular, we investigate the composition dependence of the yield strength of these alloys as a function of composition in the 5%-20% Cr range. We employed classical MD simulations to analyze the velocities of straight edge, screw, and mixed dislocations in <111>{110} primary slip systems in Fe-Cr alloys in this composition range. These velocity regimes were then incorporated into OpenDiS – DDD framework in the form of a piecewise-linear mobility law to simulate plastic deformation. The effects of composition were studied in terms of (i) the influence of Cr concentration on yield strength, and (ii) the impact of the composition-dependent mobility law on yielding and hardening behavior. It was observed that flow stress of these alloys is strongly dependent on composition. To further deconstruct the composition-dependent flow stress, we analyzed the distribution of dislocation characters across the simulation domain in conjunction with their velocity flux contributions to the plastic strain rate.