High cycle fatigue and corrosion behaviors of Mg3Zn/HA biodegradable composite

In this study, the effects of adding sub-micron hydroxyapatite (HA) particles were investigated on high cycle fatigue (HCF) and corrosion behaviors of Mg3Zn magnesium alloy. To this end, the Mg3Zn alloy and Mg3Zn/2.5 wt%HA bio composite were fabricated using mechanical-electromagnetic stir casting method followed by hot extrusion process. The results of the microstructural evaluation showed that grain refinement occurred in the composite by 48 % and Vickers microhardness increased approximately by 12 %. According to the results of the pH and weight loss measurements during the immersion tests, the presence of sub-micron HA particles increased the pH of the simulated body fluid (SBF) containing the composite specimens because of the micro-galvanic corrosion between the primary phase and the secondary phase of Ca2Mg6Zn3 in the matrix. However, a thicker protective surface layer formed on the composites, which may lead to a more desirable protection in the longer immersion time, compared to those of the monolithic alloy. Under the tensile monotonic load, the composite exhibited a moderate increase in the yield stress and a reduction in the ultimate tensile strength and the maximum strain at fracture, while the yield stress amelioration is more considerable under the compressive monotonic load. In comparison to the monolithic alloy, an improvement was observed in the high cycle fatigue behavior of the composite, which could be attributed to the yield stress enhancement, retarding the crack initiation under the same stress amplitudes.