Hydroxyapatite Reinforced Magnesium Alloy Composites Using the Ultrasonic-Assisted Rheo-Squeeze Casting Technique: Microstructural and Mechanical Performance Evaluation for Bone Fixture Applications

Magnesium-based biomaterials have recently been in the research spotlight in the field of biomedical engineering owing to their properties, such as density and biocompatibility that closely align with those of human bone. However, poor strength and rapid degradation impede their application as bone support fixtures. The present research aims to tailor the properties of Mg by using a novel ultrasonic-assisted rheo-squeeze casting approach. To satisfy the demand, pure Mg (Mg), MHA (Mg/5%HA), MZHA (Mg-1%Zn/5%HA/), and MSHA (Mg-1%Sn/5%HA) were fabricated, and various mechanical tests were conducted to assess the composite's mechanical properties, including its microhardness, tensile strength, compressive strength, flexural strength, and impact strength. The microstructural and fractured morphology of the composites was examined by scanning electron microscopy (SEM), whereas their elemental composition was analyzed by field emission scanning electron microscopy (FESEM) equipped with elemental mapping. Comparing the MZHA, MHA, and pure Mg samples, the mechanical behavior of MSHA is significantly superior. This is due to composites containing Sn that possess finer-grained materials, which act as barriers to dislocation motion while increasing the strength of the materials. From the observed results, there is a significant improvement in the microhardness of MSHA of 64.5% when compared to that of pure Mg, and 42.7% compared to MHA. Furthermore, MSHA composites possess noticeable enhancements in tensile and compression performance of 80.8% and 58.3%, respectively, and 19% and 22.4% compared to MHA. Additionally, the impact and flexural performance of MSHA composites exhibit higher performance (41% and 42%) than pure Mg and 8% and 7% against the MHA composite.