Fabrication of Porous Mg–Ca–Zn Alloy by High Energy Milling for Bone Implants

Biodegradable porous magnesium-based alloys are essential in hard tissue engineering, such as mechanical support during healing process, and disappear after completion of the healing process, avoiding the secondary surgery. The present study aims to fabricate Mg–Ca–Zn degradable metallic foam implant for domestically made bone replacement. The foam was introduced through the variation of TiH₂ addition as blowing agent that will create a large volume fraction of gas-filled pores during heating. A High-Energy-Milling (HEM) was performed by a horizontal rotating cylinder ball mill with a rotation speed of 130 rpm for 48 h, with the ratio of metallic powders: balls are 3:7 followed by a compacting process. Some samples were subjected to preheating at 450 °C for 2 h before sintering process to observe its effect on pore formation of the green compact, followed by sintering at the temperature of 550 and 650 °C for 3 h. Samples sintered at 650 °C showed profuse micro-cracks, due to uncontrollable release of H₂ gas in the liquid film creating pore rupture and MgO formation that detected from XRD analysis, that impedes the sintering process. While sintering at a lower temperature showed a dependence on preheating process. The preheated samples containing MgO suffered from micro-cracking, except for sample with 3 wt% of TiH₂, where TiH₂ can act as oxygen scavenger that hinders the formation of MgO. In contrast, all samples without preheating remained intact without obvious micro-cracks. Those samples have a comparable hardness value to that of the bone. The pores in the materials measured according to Archimedes procedure behave as gypsum. Thus concerning mechanical properties, the samples can be regarded as bone implants.