Twin-boundary and precipitate interaction in Mg–Al alloy: an MD study

Abstract

Abstract Strengthening of Mg-alloys by precipitation is much less efficient than in other metallic alloys (e.g. Al) as the Mg17Al12 precipitates grow as thin plate or lozenge shaped or long rod shape parallel to the basal plane. Recently atomistic simulations reveal that the dislocation-precipitate interaction is very week to claim for the precipitation hardening mechanism. However, the interaction of twin-boundary with the Mg17Al12 precipitate remains unexplored using atomistic simulation. In the present study we focus on the twin-boundary/precipitate interaction at different temperatures, precipitate sizes and varied applied loads, carried out using classical molecular dynamics methodology. In particular, the activation energies necessary to overcome various precipitates are determined as a function of the temperature, precipitate size and applied load. The velocity profile of the twin is calibrated with these different external conditions. An attractive nature of interaction has been observed while the twin-boundary comes closer to the precipitate and a network of dislocations are observed when the twin-boundary bypass the precipitate, as manifested through our atomistic microstructures. These results provide valuable information about the precipitate hardening mechanisms and suggested new avenues to improve the mechanical properties of Mg–Al alloys.