Microstructure Evolution and Properties of beta-TCP/Mg-Zn-Ca Biocomposite Processed by Hot Extrusion Combined with Multi-Pass ECAP

To further improve the comprehensive performance of Mg-based alloy, hot extrusion combined with multi-pass equal channel angular pressing (ECAP) was applied to process Mg-3 wt%Zn-0.2 wt%Ca alloy and 1 wt%beta-TCP/Mg-3 wt%Zn-0.2 wt%Ca biocomposites. The microstructure evolution, mechanical properties, corrosion behavior, and cell biocompatibility of the experimental specimens were systematically investigated. The average grain size of 13.4 +/- 0.6 mu m in MgZnCa alloy and 9.6 +/- 0.3 mu m in composites materials can be achieved by six ECAP passes. The uniaxial compressive strength (UCS) of 388.4 +/- 7.3 MPa and the strain at failure of 14.3 +/- 1.5% were confirmed in MgZnCa alloy, while the UCS of 405.3 +/- 7.4 MPa and the strain at failure of 9.8 +/- 1.9% were achieved by the addition of beta-TCP after six ECAP passes. In spite of different compositions, the minimum corrosion rate of 0.895 mm center dot Y-1 and 1.117 mm center dot Y-1 can be achieved by two ECAP passes at 593 K. The cytocompatibility evaluation revealed that the experimental materials processed by six ECAP passes had no significant cytotoxicity to L929 cells, and the addition of beta-TCP improved the cytocompatibility.