Microstructure And Properties Of Biomedical (HA+?-TCP)/Mg Interpenetrating Composites

In order to obtain ideal bone tissue substitutes with controllable degradation rate, this paper prepared a composite by penetrating magnesium alloy melt into porous biphasic bioceramic scaffold, with an expectation to take complementary advantage of all three kinds of materials, namely hydroxyapatite, ?-calcium phosphate and magnesium alloys.The ?-TCP and HA powder synthesized by wet chemical precipitation was used to fabricate porous bioceramic scaffolds with HA/?-TCP ratio of 10/90?20/80?30/70?40/60 and 50/50.Then suction casting was adopted to penetrate magnesium alloy melt into these porous bioceramic scaffolds. Magnesium alloys in this paper are Mg-2Y, Mg-5Sn and Mg-3Zn binary alloys. The microstructure, mechanical properties and corrosion behaviors of composites have been evaluated by SEM, XRD, EDS, compression test and immersion test in vitro, etc.The results indicated that the composite prepared was of an interpenetrating network structure in which magnesium alloy melt not only penetrating into the macro porous but also into the micro porous between ceramic particles. The HA/?-TCP ratio was a critical influence for the alloy-ceramic interface: increasing HA proportion led to a well ceramic particle dispersion and lower wettability of alloy melt on ceramic particles. When the HA/?-TCP ratio reached 50/50 high, alloy melt failed in fully penetrating into the micro interspaces of ceramics, resulting in poor interface.The compressive strength of Mg-2Y, Mg-5Sn and Mg-3Zn alloys were 226MPa?228MPa and 260MPa respectively while that of bioceramic scaffolds were all under 1.5MPa,and for composites,were between 114MPa and 196MPa, which is a satisfactory for bone tissue substitutes materials.The electrochemical results depicted a vulnerable corrosion of magnesium alloys than composites. The investigation into the corrosion mechanism was carried out to find that: the matrix alloys were corroded uniformly on the surface while multiple corrosion mechanism including dot corrosion, gap corrosion and crystal corrosion were observed on the composites,especially for the (HA+?-TCP)/Mg-2Y system, in which the comprehensive co-corrosion brought out rapid corrosion, indicating a poor performance in corrosion resistance.(HA+?-TCP)/Mg-5Sn and (HA+P-TCP)/Mg-3Zn systems, low HA/?-TCP ratio in materials were followed by dot corrosion dominant destruct, and high HA/?-TCP ratio by gap corrosion dominant damage of the materials, while the medium HA/?-TCP ratio, performed well in corrosion resistance.