Reversible plastic strain during cyclic loading-unloading of Mg and Mg-Zn alloys

Large hysteresis loops are observed during cyclic loading-unloading of Mg and Mg-Zn alloys. This is true for both tension and compression cycling, for grain sizes between 25 and 670 Rm, and for Zn contents between 0 and 6 mass%. The loops are ascribed to anelasticity resulting from elastic (10 121 twinning. The anelastic strain increases with the strain and reaches a maximum at strains between about 1 and 2%. For a given total strain, the amount of anelastic strain increases with decreasing grain size, and decreases with increasing Zn content. The maximum observed anelastic strain is about 0.3% for pure Mg, decreasing with the solute content to about 0.2% for Mg-6 mass% Zn. The phenomenon is discussed in terms of the effect of solute content and grain size on the formation and stability of twins. (C) 2006 Elsevier B.V. All rights reserved.