چكيده به لاتين
Magnesium matrix composites have recently received much attentions from automotive, aerospace and medical industries due to their unique mechanical properties, high strength to weight ratio, low density and desirable machinability. Since magnesium is one of the vital elements for human metabolism and has similar mechanical properties to human bone, its medical applications have been developed. Moreover, one of the characteristics of biocompatible magnesium alloys is their biodegradable ability. As a result, they can be used to produce bone fixation and orthopedic implants, resulting in elimination of the secondary surgeries. In this thesis, Mg-3Zn magnesium alloy matrix composite has been reinforced by 2.5 wt% of hydroxyapatite (HA) sub-micron particles (with an average size of 500 nm) using mechanical-electromagnetic stir casting followed by hot extrusion process. Regarding the importance of the corrosion and fatigue behaviors of the composites according to their potential applications, fatigue and corrosion behaviors of Mg-3Zn/2.5 wt% HA have been studied. Furthermore, tensile and compressive properties as well as microhardness have been evaluated. In addition, the effect of heat treatment on the composite behavior has been investigated. In this regard, the specimens were heat treated for 24 hours at 400℃. The results exhibit that the presence of the hydroxyapatite particles increases the mechanical properties of the composite compared to those of the monolithic alloy. Tensile yield stress and microhardness of the composite (without heat treatment) have improved by 9.6% and 11.6% respectively, in comparison to the untreated alloy specimens.
Furthermore, the alloy offers more desirable corrosion properties. Applying the heat treatment process decreases the corrosion rate of the composite. Corrosion resistance of the composite has been improved by 16.5% using the heat treatment process.
