The effect of high yttrium solute concentration on the twinning behaviour of magnesium alloys

The deformation behaviour of two single phase binary alloys, Mg-5Y and Mg-10Y, have been examined. In compression, two twin types were observed, the common {10 (1) over bar2} twin as well as the less common {11 (2) over bar1} extension twin. It is shown that the {11 (2) over bar1} twin is much less sensitive to solute concentration than the {10 (1) over bar2} twin, and it is suggested that the simple atomic shuffle of the {11 (2) over bar1} twin reduces the solute strengthening imparted by Y additions. The common {10 (1) over bar2} twin showed significant hardening as a result of alloying with Y. An analysis of solute behaviour has indicated that of the four chemical parameters investigated, i.e. atomic size, shear modulus, electronegativity and solute distribution, it appears to be the larger atomic radius of Y compared to Mg that increases the stress required to activate the {10 (1) over bar2} twin. It is suggested that the large atomic radius inhibits the atomic shuffling process which accompanies the twinning shear in this twin type. Crown Copyright (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.