Influence of Nonglide Stress on The Structure and Mobility of Pyramidal-I and -II 〈c + a〉 Edge Dislocations in Magnesium

Abstract

Herein, molecular dynamics simulations were performed to investigate the structure and slip behavior of 〈c + a〉 edge dislocations on the pyramidal-I (Pyr-I) plane in magnesium (Mg), which were compared to those on the pyramidal-II (Pyr-II) plane. 〈c + a〉 dislocations on pyramidal planes are metastable and transition into sessile, typically sessile 〈c〉 and glissile 〈a〉basal dislocations (basal-dissociated 〈c〉 + basal 〈a〉), or a dissociated 〈c + a〉 dislocation along the basal plane (basal-dissociated 〈c + a〉 and its derivative structure). This transition occurs at temperatures of >100 and >400 K for Pyr-I and -II 〈c + a〉 edge dislocations, respectively, in the absence of shear deformation along the slip direction, except under large nonglide stresses. The critical resolved shear stress (CRSS) of the slip plane where Pyr-I 〈c + a〉 edge dislocations glide at 10 K increases with increasing compressive or tensile strains normal to the slip plane and exhibits a minimum value of ~486 MPa. Similarly, the CRSS for Pyr-II 〈c + a〉 edge dislocations decreases with increasing compressive strains normal to the slip plane and exhibits a maximum value of ~149 MPa at 10 K. Our findings provide insights into the design of ductile Mg alloys.