INFLUENCE OF INTENSIVE PLASTIC DEFORMS BY EXTRUSION ON MICROSTRUCTURE AND PHYSICO-MECHANICAL PROPERTIES OF Mg-Y-Nd AND Mg-Ca ALLOYS

10.25712/ASTU.1811-1416.2022.04.007

Abstract

The effect of extrusion on the mechanical properties of biomedical alloys based on Mg-Y-Nd and Mg-Ca systems has been studied. The alloys were deformed by hot backward extrusion, accumulated deformation was e=1.46. It is shown that as a result of extrusion a dispersed particle-strengthened Mg₂₄Y₅ and Mg₂Ca bimodal structure consisting of magnesium phase grains with average size of 14 and 9 microns correspondingly for Mg-Y-Nd and Mg-Ca alloys and a-phase with size less than 1 µm for both alloys is formed, the volume fraction of which is 22 and 50 %, respectively. The bimodal structure in the Mg-Y-Nd and Mg-Ca alloys provides 1.5 and 2.5 times higher yield strength and 1.8 and 6.3 times higher ductility, respectively, which is due to substructure strengthening, redistribution of phase composition and emerging texture. It is shown that extrusion treatment of Mg-Y-Nd alloy does not result in worse corrosion resistance of the alloy in physiological solution (0.9 % NaCl solution in distilled water, pH = 7) unlike the Mg-Ca alloy where the presence of a larger volume fraction of ultra-fine grains and intergranular boundaries contributes to a significant increase in corrosion rate.