Deformation behavior of Mg–5Y–2Nd–0.5Zr alloys with different Sm additions

Herein, we studied the microstructural evolution and deformation behavior of aged Mg–5Y–2Nd–xSm–0.5Zr (x = 1, 3, and 5 wt%) alloys during uniaxial compression at room temperature by transmission electron microscopy and quasi-in-situ electron backscatter diffraction techniques. The microstructures of Mg–5Y–2Nd–xSm–0.5Zr alloys are refined by the addition of Sm, with more occurrences of Mg(Nd, Sm) precipitates. The average grain size decreased significantly with increasing Sm content, from 80.4 µm (1 wt% Sm) to 64.8 µm (3 wt% Sm) and 50.0 µm (5 wt% Sm). The Mg–5Y–2Nd–3Sm–0.5Zr alloy exhibited a maximum compressive strength of 390.1 MPa and a maximum strain (ε) of 0.103 at room temperature; {10−12} tensile twinning and dislocation slips are the main plastic deformation modes of Mg–5Y–2Nd–xSm–0.5Zr alloys during compression at room temperature. A number of<a>and<c + a>dislocations were observed in the aged Mg–5Y–2Nd–3Sm–0.5Zr alloy. The optimized ductility value is attributable to grain refinement; elemental Sm promotes the activation of the non-basal<c + a>slip dislocations and interactions between twins and<c + a>dislocations. The strengthening mechanism mainly includes solid solution, fine-grain, and precipitation strengthening.