[SY-C1] Symposium C-1

[SY-C1] Kinetic Monte Carlo model of screw dislocation-solute coevolution in W-Re alloys

Invited

Yue Zhao¹, Lucile Dezerald³, ^○Jaime Marian^1,2 (1.Dept. of Materials Science and Engineering, University of California Los Angeles, United States of America, 2.Dept. of Mechanical and Aerospace Engineering, University of California Los Angeles, United States of America, 3.Institut Jean Lamour, University of Lorraine, France)

Dislocation-solute interactions are at the heart of many important processes in materials science and metallurgy, such as solid solution strengthening, dynamic strain ageing, pipe diffusion, etc. In body-centered cubic (bcc) metals, plastic flow at low-to-intermediate homologous temperatures is controlled by screw dislocation glide. In this temperature range, both solute diffusion and dislocation motion are thermally activated processes sensitive to stress, and the overall plastic behavior can be reduced to the study of a single screw dislocation interacting with solutes. This interaction is complex, and can result in material softening and/or hardening depending on temperature and solute concentration. Here, we solve this coupled transport problem for W-Re alloys in three dimensions using kinetic Monte Carlo simulations. The interaction between Re solutes and dislocation segments is captured via the elastic dipole tensor, parameterized with electronic structure calculations, while dislocation segment-segment interactions are described using nonsingular elasticity theory. We find that there are two clearly defined regimes as a function of Re concentration. For low values, the softening effect on kink-pair nucleation energy overcomes kink-solute collisions, leading to an overall reduction in alloy strength compared to pure W. The situation is reversed at higher concentrations, resulting in overall hardening. Our results are in reasonable agreement with several experimental measurements, and point to the intrinsic nature of the softening/hardening transition in W-Re alloys. We also report on preliminary simulations of dislocation-impurity interactions in the W-Cu system, where the basic mechanisms behind dynamic strain aging in substitutional bcc solid solutions starts to manifest itself in a specific temperature range.