Effect of Si and HA on the Mechanical Characteristics of Spark-Plasma-Sintered Mg–Zn–Mn–(Si–HA) Composites

Mg–Zn–Mn-based biocomposites hold prospects as potential orthopedic material. The composition of these composites can be modulated, based on applications, by selective elemental alloying. Towards that, the addition of silicon (Si), hydroxyapatite (HA), or both is considered, followed by the consolidation method, such as spark plasma sintering (SPS). In this study, the micro-mechanical properties of Mg–Zn–Mn–(Si–HA) composites were investigated through the micro-pillar compression method. The effect of Si and HA incorporation on the mechanical characteristics and deformation mechanism was also elucidated. The microstructure of the composite presents porosity, together with different bioactive phases, such as Mg–Zn, CaMg, Mn–P, MgSi2, Mn–Si, Mn–CaO, CaMgSi, and Ca–Mn–O. Such porous structures were determined to facilitate cell growth when used as an implant, particularly for musculoskeletal-related disabilities. The yield stress (YS) and compressive stress of the Mg–Zn–Mn–Si–HA were about 1543 ± 99 MPa and 1825 ± 102 MPa, respectively. These values were about 5.8 and 4.8 times higher, respectively, than those of Mg–Zn–Mn–HA composites (266 ± 42 MPa and 380 ± 10 MPa, respectively), and the same was observed for the elastic modulus. Besides that, alloying with HA and Si alters the deformation mechanism from brittle (for Mg–Zn–Mn–Si composites) or ductile (for Mg–Zn–Mn–HA composites) to predominant ductile failure without compromising the attained mechanical properties.