Atomic simulations of the effect of Y and Al segregation on the boundary characteristics of a double twin in Mg
N Miyazawa and S Suzuki and M Mabuchi and Y Chino, JOURNAL OF APPLIED PHYSICS, 122, 165103 (2017).
There is usually a tradeoff between the strength and the ductility in solute strengthening of metallic materials. However, magnesium is an exception. A 10 (1) over bar1-10 (1) over bar2 double twin (DT) provides a fracture-initiation site in Mg. Hence, an investigation on effects of segregations on facture at the DT will give a clue for understanding an exception of Mg to the tradeoff relation. In the present work, we investigated segregation behavior of Y and Al at the DT and interactions of a screw dislocation with segregated DTs by Monte Carlo (MC) and molecular dynamics (MD) simulations. The MC simulations showed that the volumes of the atomic Voronoi polyhedron were changed by Y segregation, while the anisotropic factors of the atomic Voronoi polyhedron were changed by Al segregation. Also, the MD simulations indicated that Y segregation induced emission of twinning dislocations from the DT, while Al segregation suppressed the motion of the twinning dislocation. Thus, the boundary characteristics of the Y-segregated DT were different from those of the Al-segregated DT because the dominant factor is the mechanical effect for the Y-segregated DT and the chemical effect for the Al-segregated DT. However, the events caused in the segregated DTs can lead to limited pile-up of twinning dislocations at the triple junctions of boundaries, resulting in ductility enhancement by alloying. Published by AIP Publishing.
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