Magnesium Strengthening in 3D Printed TCP Scaffold Composites

This study reports the production of a Mg/15%β-tricalcium phosphate Ca3(PO4)2 composite by combining direct ink writing for the β-TCP preform and liquid infiltration technique to obtain a continuous metal matrix composite. The influence of the volume fraction of β-TCP and the in situ reaction between ceramic and metal on the microstructure and mechanical properties were investigated in detail. The β-TCP preform was uniformly distributed in the matrix, forming a continuous three-dimensional (3D) network. The obtained composite was characterized by means of relative density (He pycnometry), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electron spectroscopy (EDX). The results suggested that a highly densified composite was processed. Three phases were identified as products generated by an exothermic reaction (Mg2Ca, CaO, and MgO); based on this, the chemical reaction mechanism for MgO formation was proposed. The compression and hardness tests showed that the Mg/15%β-tricalcium phosphate Ca3 (PO4)2 composite significantly improved its mechanical properties, i.e., 27% and 15% higher than pure Mg in compressive strength and yield strength, respectively. This behavior was attributed to the high densification of the resulting composite, strong chemical interfacial bonding, phase dispersion hardening (in situ phase formation), and the geometry and continuity of the reinforcement. These provided good load transfer from the Mg matrix to the reinforcement and contributed as strengthening mechanisms. The results reported in this investigation can help to design Mg/calcium phosphate continuous composites for biomedical applications.