Dynamic precipitation in an Mg-Gd-Zn-Zr alloy during hot compression at 350 and 450 and at strain rates of 0.001-0.1 s−1 is investigated. The deformation conditions were designed such as to promote twinning or slip of dislocations. The results indicated that both twinned and non-twinned grains were present at 350, with the extent being a function of the applied strain rate. The formation and propagation of ̅ ̅ primary tensile twins within the twinned grains was identified as being at root of the twin-assisted precipitation phenomenon. The precipitates had spherical-morphology in the twinned grains whereas parallel arrays of rod-shaped precipitates formed in the non-twinned grains due to dynamic precipitation on the slip bands and the stacking faults. Twin-assisted precipitates were suppressed by increases in the strain rate at 350 because of the shorter time required for solute element diffusion towards the nucleated precipitates at that temperature. Increasing the deformation temperature to 450 changed the dominant deformation mechanism from twinning to slip of dislocations, resulting in the formation of rod-shaped precipitates similar to those observed in non-twinned grains at 350. An EBSD analysis was used to study the dominant deformation mechanism as a function of the Schmid factor, and the twinning deformation mechanism was found to be predominant in the grains having a lower Schmid factor.

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