Improving Mechanical Properties of Mg-Al-RE Alloys with the Formed Dimples of Al10Mn2RE Particles and Activated Pyramidal Slip with Mn Additions.

Abstract

The effects of Mn addition on the room temperature tensile strength and deformation mechanisms of as-cast Mg-8Al-1Nd-1.5Gd-xMn alloys (x = 0, 0.3, 0.5, 1.0 wt.%) are investigated in this paper. The results indicate that the addition of Mn contributes to the precipitation of Al-Mn-RE intermetallics and the refinement of α-Mg matrices, thereby improving the tensile strength of the 1.0 Mn alloy at 190 MPa. The fracture mechanism of Mn-containing alloys transforms from a cleavage fracture to a ductile fracture as the Mn content increases from 0.3 to 1.0 wt.%. The presence of intermetallic particles in the dimples confirms the hindrance effect of Al10Mn2 (Nd,Gd) on dislocation slips. The novel technology of in-grain misorientation axes (IGMAs) is used to identify activated slip modes and deformation twins. It can be concluded that the activated pyramidal <a> slip during tensile deformation significantly promotes the ductility of the 1.0 Mn alloy with an elongation rate of 9.8%. It is worth noting that reducing the coarse 101¯2 tensile twins and enhancing the proportion of 101¯1 compressive twins and 101¯1-101¯2 double twins contributes to maintaining the continuous plastic deformation of Mg alloy.