Activation of slip and enhanced ductility in as-extruded Mg-Gd-Y-Nd alloys through Si addition

Abstract Low-cost Si was added to Mg-8Gd-4Y-1Nd alloys to improve their ductility. With the Si increased from 0 to 1.0 wt. %, the elongation increased from 8.7 % to 17.1 % for as-extruded Mg-8Gd-4Y-1Nd alloys. Microstructures results indicated that the formation of GdSi and Y5Si3 intermetallic phases increased significantly with the Si addition, which was shown to promote the random orientation of grain structures. As Si works as substitutional atoms in Mg alloys can decrease the first intrinsic stacking faults (I1SF) energy, the pyramidal dislocation was activated during deformation, thus the {0001}Mg basal plane deviate from the extrusion direction and alter to random textures. Activating both the pyramidal and basal slip provided more independent slip systems during deformation and caused more stress accumulation, which exceeded the critical shear stress (CRSS) for tensile twinning. The simultaneous activation of the pyramidal slip and tensile induced twinning improved the ductility of the Mg-8Gd-4Y-1Nd-1.0Si alloy.