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In wrought magnesium alloys, room temperature plasticity is largely controlled by limited slip systems such as basal slip and tension/compression twins. The insufficient number of active slip systems limits strength and ductility preventing broader structural applicability of Mg-alloys. Hence, we employ first-principle calculations to investigate the effects of Y and Al alloying elements on shearability and dislocation motion on various slip systems through ideal shear resistance and generalized stacking fault energy calculations. Yttrium is seen to lower the ideal shear resistance and dislocation motion energetics on all the slip systems. On the other hand, aluminum increases the ideal shear resistance but decreases the energy barrier for dislocation motion on various slip systems. The profound effects of solute addition result from the charge transfer between the solute atom and surrounding magnesium atoms.
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Critical Shape for the Growth of Grain Boundary Twin Embryos in Mg and Mg Alloys: Crystal Plasticity Modeling
Application of polycrystalline hexagonal close packed (HCP) metals in engineering designs has been constrained by their anisotropic responses due to twinning and limited plasticity. In deformation, twins most often initiate at grain boundaries (GBs), and thicken and propagate across the grain. In this work, the GB twin embryos in Mg and Mg alloys, and the conditions that influence their propagation are investigated. Using a micromechanical crystal plasticity model, the role of embryo shape on the driving forces prevailing at the embryo boundaries that could support its expansion is studied. The modeled embryos are either planar, extending more in the shear direction than normal to the twin plane, or equiaxed. Results show that the thinner the embryo, the greater the driving forces for both thickening and forward propagation. Alloys with low prismatic-to-basal critical resolved shear stress (CRSS) ratios promote embryo thickening and large CRSS values for the slip mode that primarily accommodates the twin shear encourage propagation. The neighboring grains with orientations that enable local accommodation of the embryo twin shear by pyramidal slip promote forward propagation but have little effect on thickening. When two like embryos lie along the same GB, their paired interaction promotes forward propagation but hinders thickening.
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- Award ID(s):
- 2051390
- PAR ID:
- 10411838
- Date Published:
- Journal Name:
- Alloys
- Volume:
- 1
- Issue:
- 2
- ISSN:
- 2674-063X
- Page Range / eLocation ID:
- 212 to 231
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3390/alloys1020013
