Effect of Severe Plastic Deformation by Extrusion on Microstructure and Physical and Mechanical Properties of Mg–Y–Nd and Mg–Ca Alloys

Abstract

The effect of extrusion on the mechanical properties of biomedical alloys based on Mg–Y–Nd and Mg–Ca systems is studied. The alloys are deformed by hot backward extrusion, accumulated deformation is e = 1.46. It is shown that the extrusion leads to the formation of bimodal structures that are disperse-strengthened by Mg₂₄Y₅ and Mg₂Ca particles and consist of α-phase magnesium grains with mean sizes of 14 and 9 μm for Mg–Y–Nd and Mg–Ca alloys, respectively, and α-phase grains with a size of less than 1 µm for both alloys (the volume fractions are 22 and 50%, respectively). The bimodal structure in the Mg–Y–Nd and Mg–Ca alloys provides an increase in the yield strength by factors of 1.5 and 2.5, respectively, and an increase in ductility by factors of 1.8 and 6.3, respectively, due to substructure strengthening, redistribution of phase composition, and emerging texture. It is shown that the extrusion treatment of the Mg–Y–Nd alloy does not result in worsening of corrosion resistance of the alloy in physiological solution (0.9% NaCl solution in distilled water, pH 7) unlike the Mg–Ca alloy for which the presence of a larger volume fraction of ultrafine grains and intergranular boundaries leads to a significant increase in corrosion rate.