Compression behavior of cast high-porosity magnesium with directionally oriented structure

The influence of different porosity levels of magnesium gasars manufactured with the use of the Bridgman-type directional solidification method on their compression behavior was investigated. The cross-section structure perpendicular to the height of the produced gasars ingots was characterized using X-ray computed tomography (CT). These results indicated that gasars with porosities of 30%, 36%, 39%, and 48% were obtained, and those with porosities of 30% and 36% had a homogenous porosity distribution and the uniform diameter of the pores. Compression tests were carried out to compare the mechanical properties of the manufactured gasars vs cast porosity-free magnesium. The gasar with 30% porosity achieved the highest compressive strength R c of all the tested gasars ingots, which was 107 MPa. In addition, when the compressive strength was calculated for the sample cross-section, excluding its porosity, the modified compressive strength MR c of 152 MPa was obtained for the gasar with 30% porosity, and it was about 8.5% higher than the compressive strength of monolithic porosity-free magnesium. Moreover, taking into account the density of tested material, the gasar with 30% porosity achieved the highest specific strength and the highest energy absorption capacity among all the tested magnesium gasars. For the examined materials, numerical simulations of the compression behavior were performed, and the results obtained are discussed in terms of the mechanism controlling the strengthening process in a high-porosity magnesium with directional oriented structure.