Room-temperature plastic deformation of single crystals of Mg17Al12 with the body-centered cubic α-Mn (A12) type structure

The deformation behavior of single crystals of Mg 17 Al 12 has been investigated by micropillar compression at room temperature as a function of crystal orientation and specimen size. Three slip systems, {110}<111>, {110}<001> and {110}<110>, are identified to operate in crystal orientations in the middle of the stereographic triangle, close to [ 1 ‾ 11] and [001], respectively. The latter two slip systems are identified in the present study for the first time. The averaged CRSS values obtained for micropillar specimens in the size range of 1.5 to 10.6 μm do not vary significantly with slip system, and they are 295, 325, and 300 MPa for {110}<111>, {110}<001>, and {110}<110> slip, respectively. While the specimen size dependence of yield stress is negligibly small for {110}<001> and {110}<110> slip, that for {110}<111> is comparatively large. The bulk CRSS values estimated by the extrapolation of the size-dependent yield stress are 200±35, 305±50, and 280±55 MPa for {110}<111>, {110}<001>, and {110}<110> slip, respectively. As predicted by DFT (density functional theory) calculations, there are some stacking faults of sufficiently low energy, leading to two- and three-fold dissociation for the dislocation with b (Burgers vector)=1/2<111> carrying {110}<111> slip and the dislocation with b=[110] carrying {110}<110> slip, respectively. The deformation behavior of Mg 17 Al 12 is compared to that of isostructural α-Mn, in particular, in terms of the existence of low-energy stacking faults and the resultant dislocation core dissociation/spreading.