New porous Mg composites for bone implants

Various porous Mg alloys and composites have been fabricated to date. However, typically they have unsatisfactory mechanical properties, particularly in load bearing applications. In the current work, porous magnesium-niobium (Mg-Nb) and magnesium-tantalum (Mg-Ta) composites were fabricated via a combination of mechanical milling and powder metallurgy processes. The effect of Nb and Ta contents on the porosity, pore size and mechanical properties of the porous Mg composites was investigated. The microstructural observations show irregular cell shapes, including micro- and macro-pores in the porous materials. The number and size of macro-pores increased with an increase in the amount of reinforcement (Nb or Ta). The mechanical properties of the porous Mg composites increased with an increase in reinforcement contents up to 2 wt% and then decreased. The type, particle size and position of reinforcements influence the strength of porous composites. Fractography of the compressed porous samples showed that in porous Mg-Nb and Mg-Ta composites, cracks are initiated from pores and gaps between Mg powders and propagated through cell walls and cell edges. The strength of these porous Mg composites is comparable to that of human bone.