Effect of plate-shaped particle distributions on the deformation behaviour of magnesium alloy AZ91 in tension and compression

The magnesium alloy AZ91 was hot rolled and annealed to produce a plate with a strong basal texture. The resultant plate was mechanically tested in five different test orientations in the solution-treated, underaged, peak-aged and overaged conditions. The critical resolved shear stresses for activation of basal slip, prismatic slip and twinning were then estimated for each of the ageing conditions. We found that the age hardening of the slip systems is consistent with Orowan hardening, but that this theory significantly underestimates the hardening of the {1 0 (1) over bar 2} twin system. It is proposed that back stresses and hardening of the slip systems that accommodate twinning also contribute to precipitate hardening of the twin system. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.