Improved mechanical properties and strengthening mechanism with the altered precipitate orientation in magnesium alloys

Aging prior to twinning deformation was proposed to alter the precipitate orientation of the plate-shaped β-Mg17Al12 from (0002)α basal planes (named basal plates) to {101¯0}α prismatic planes (named prismatic plates) in AZ31 Mg alloy. The experimental results showed that the compressive yield strength (CYS) of the sample containing prismatic plates increased 40 MPa and the compression ratio raised by 22% compared to that containing basal plates. The underlying strengthening mechanism was analyzed via a yield strengthen (YS) model with a function of grain size, precipitate characters (size, oritention, fraction) and Schmid factor (SF). It revealed that the improvement of CYS was mainly attributed to the altered precipitate orientation and refined grain size produced by twinning deformation. Particularly, the prismatic plates always have a stronger hardening effect on basal slip than basal plates under the same varites of precipitate diameter and SF. Besides, the decreased CRSS ratio of prismatic slip to basal slip revealed that the activity of non-basal slip in Mg alloy might be enhanced. More activated slip systems provided more mobile dislocations, contributing to the large compression ratio of the Mg rolled sheet with prismatic plates.