Effects of lattice parameter changes on critical resolved shear stress and mechanical properties of magnesium binary single crystals

Abstract

The effect of lattice parameter changes on the critical resolved shear stress has been investigated by using single crystals of Mg binary alloys as well as a pure Mg. A series of tensile tests has been conducted at room temperature (RT), 150 degrees C, 250 degrees C and 350 degrees C under the strain rate of 5 x 10(-3)/s. The critical resolved shear stresses (CRSS) for basal slip were then found not to depend much on test temperatures, but binary solutions exhibited higher CRSS compared to that of pure magnesium. The binary alloys of Mg-Zn and Mg-Li exhibited the highest and lowest CRSS, having the largest and smallest change in lattice parameters, respectively. A modified size misfit parameter was then proposed in this study to express the friction mechanism in HCP crystals quantitatively, which originates from the atomic size misfit between Mg and solute atoms. The yield and ultimate tensile strengths of poly crystalline Mg were also obtained to compare with those of single crystals. The yield strengths of Mg poly crystals were found to depend on the CRSS for basal slip, while the ultimate tensile strengths to depend on the CRSS of non-basal slips. The effect of axial ratio changes on texture development has also been investigated in this study. The axial ratio, (c/a) was found to either increase or decrease by adding the solute atoms of Al or Li to develop a stronger or weaker basal pole, respectively. Addition of Zn exhibited, on the other hand, no effect on the texture development. (C) 2012 Elsevier B.V. All rights reserved.