{1012} Twinning in magnesium-based lamellar microstructures

The magnesium-based alloy Mg–9Al–1Zn has been extruded and heat treated to produce a dense population of lamellar plate-shaped particles. In compression with a testing orientation well aligned for prolific {1012} twinning, precipitation resulted in a significant increase in the yield point, but there was no change in the volume fraction of twins that were produced. It is proposed that the larger number of smaller twins observed in the aged condition is the result of inhibition of twin growth by the particles.