Microstructure and properties of β-TCP / Zn - 1Mg composites processed by hot extrusion combination of multi-pass ECAP

To further improve the comprehensive service performance of Zn, hot extrusion combined multi-pass equal channel angular pressing route were applied to process Zn-1(wt%)Mg alloy and 1(vol%)β-TCP/Zn-1Mg composites. As-cast cylinders specimens with a diameter of 60 mm were finally processed to the ECAP-processed specimens with the dimensions of 15 mm × 15 mm × 120 mm. The evolution and corresponding mechanism of the microstructure, mechanical properties, corrosion behavior, and biocompatibility of 1β-TCP/Zn-1Mg composites and Zn-1Mg components were systematically investigated. As a result, compared with Zn-1Mg alloy, the grain refinement effect of ECAP was enhanced in the 1β-TCP/Zn-1Mg composites with exact the same ECAP conditions. Among all the experimental specimens, the minimum average grain size of 3.0 ± 0.3 µm was achieved in 1β-TCP/Zn-1Mg composites processed by 8 ECAP passes. With the increase of ECAP processing times, the texture strength increased, and the texture direction changed to be (0 0 0 1) base plane parallel to TD-axis. Consequently, the 1β-TCP/Zn-1Mg composites after 8 passes of the ECAP process exhibited the highest compressive yield strength (CYS) of 288.05 ± 6.87 MPa and an elongation greater than 50%. Moreover, these composites also showed a moderate degradation rate of 0.04496 mm·y−1 in the simulated body fluid solution. The in vitro cytotoxicity and cytocompatibility evaluation revealed that both ECAP-processed Zn-1Mg alloy and 1β-TCP/Zn-1Mg composites showed non-cytotoxicity to MC3T3-E1 cells, and the addition of β-TCP could improve the biocompatibility of the experimental materials. Above all, the combination of hot extrusion and ECAP should be a useful route to obtain biodegradable Zn-based materials with excellent comprehensive service performance as orthopedic implants. The 1β-TCP/Zn-1Mg composites, which were processed by hot extrusion and subsequent 8 passes ECAP, exhibited the highest CYS, moderate degradation rate, and good biocompatibility, should be a promising candidate for the application of bone repair and bone replacement.