Characterization of advanced Mg-Li-Y alloys for application as biodegradable biomedical implants

Abstract

To determine the effect of grain refinement, down to sub-micrometer range, in mechanical, corrosion and biocompatibility properties of magnesium alloys. There is significant interest in developing better materials for implant applications. Among the biomaterials, metals play a significant role in structural applications where load bearing capacity and toughness are required. Early metallic biomaterials were basically inert materials such as stainless steel and titanium. Later, surface treatments were used to enhance the interaction of the implant with the surrounding tissue. Recent interest has turned into materials which are able to degrade while the surrounding tissue recovers. Magnesium is considered the top candidate for biodegradable metallic material due to high biocompatibility and high limit of daily dosage intake. However, its mechanical properties (strength and ductility) and corrosion rate needs improvement. Basically, it is of great interest to improve strength, low elastic modulus (45 a 60 GPa) and reduce corrosion rate. Many research groups have focused on evaluating the effect of alloying elements and thermo-mechanical processing in these properties. Recent investigations have shown that severe plastic deformation techniques are able to significantly refine the grain structure of magnesium and its alloys and to improve their strength. However, the effect of such processing on biodegradation is not clear yet. Also, most research has focused on conventional alloys used in structural applications which might contain toxic alloying elements. Thus, the aim of the present research is to evaluate the effect of grain refinement through different severe plastic deformation techniques in the performance of different Mg-Li-Y alloys as biodegradable material candidates. The alloys composition in the present investigation will be focused on biological application and therefore only non-toxic elements will be used. Also, the maximum alloying element content will be based on maximum daily intake of such element and the rate of degradation of the material. (AU)