The Interaction between Mg17Al12 Precipitate and {10-12} Twin in Mg-Al Alloy: A Molecular Dynamics Simulation Study

Molecular dynamics simulation was applied to investigate the interaction between precipitate and {10 (1) over bar2} twin in Mg-Al alloy in this work. Three sets of simulation including twin nucleation, propagation and growth affected by precipitate were performed. The results show the introduction of precipitate has little effect on neither the homogeneous twin nucleation at random site inside the grain nor the heterogeneous nucleation at grain boundary. During twin propagation, the blocking effect of precipitate to the twin tip depends on its size. The twin tip can bypass the precipitate when the precipitate is not long enough. When the length of precipitate is much larger than the thickness of twin, the twin tip will be completely blocked by the precipitate with elastic bending occurring at the junction. During the twin growth, it is found that the precipitate plays not only an obstacle but a source for the twinning dislocations gliding along the twin boundary. The blocking effect of precipitate on twin growth shows a size effect. The influences of width and thickness on precipitation hardening are significantly greater than that of length.