Exceptional reversed yield strength asymmetry in a rare-earth free Mg alloy containing quasicrystal precipitates

Abstract

This work reports an exceptional reversed yield strength asymmetry at room temperature for a rare-earth free magnesium alloy containing a mass of fine dispersed quasicrystal (I-phase) precipitates. Although exhibiting traditional basal texture, it owns an exceptional CYS/TYS as high as ∼1.17. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) examinations indicate pyramidal and prismatic dislocations plus tensile twinning being activated after immediate yielding in compression while basal and non-basal dislocations in tension. I-phase particles transferred the concentrated stress by self-twinning to provide the driving force for tensile twin initiating in neighboring grains, thereby significantly increasing the critical resolved shear stress of tensile twinning to possibly the level of pyramidal slip, finally leading to the dominance of pyramidal slip plus tensile twinning in texture grains. This results in a higher contribution on yield strength by ∼55 MPa in compression than in tension, which reasonably agrees with the experimental yield strength difference (∼38 MPa). It can be concluded that I-phase particles influence deformation modes in tension and in compression, finally result in reversed yield strength asymmetry.

Keywords

• Magnesium alloy
• Reversed yield strength asymmetry
• Transmission electron microscopy (TEM)
• Twinning
• Dislocations