Improving Mechanical Properties of Mg-Al-RE Alloys with the Formed Dimples of Al10Mn2RE Particles and Activated Pyramidal <a> 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 &lt;a&gt; 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.

Deformation Mechanisms of Magnesium Alloys with Rare-Earth and Zinc Additions under Plane Strain Compression

“…This, in turn, reduces the stress/strain accumulation that initiates cracking. In terms of the effects of RE on the precipitation strengthening, it was reported that intermetallics can refine the grain size of the α-Mg matrix [ 14 , 15 ], resulting in the change of fracture mode from cleavage to ductile. Furthermore, the segregation [ 16 , 17 ] and precipitation [ 18 ] of RE atoms reduce the grain boundary mobility, changing the dynamic and static recrystallization textures.…”