Deformation mechanisms and mechanical properties of porous magnesium/carbon nanofiber composites with different porosities

This study investigated mechanical properties and deformation mechanisms of porous magnesium–carbon nanofiber composites with different porosities manufactured through powder metallurgy. Compressive stress–strain curves of the samples exhibit three phases: Phase I of linear elastic deformation at low stress state, Phase II of a stress plateau, and Phase III of densification. The manufactured porous composites with different porosities show different deformation mechanisms. The composites with low porosity (i.e., 24 and 34%) manifest stretch-dominated deformation with hard (i.e., tension, compression) modes, while the composite with high porosity (i.e., 50%) demonstrates bending-dominated deformation with soft (i.e., bending) modes. The yield strength and the ultimate compressive strength decreased at an increasing rate with the increase in the porosity from 24 to 50%. Theoretical estimations were obtained for the yield strength of dense magnesium composites based on Gibson and Ashby model.