The effect of aluminium content on the bioactivity behaviour of biodegradable magnesium alloys for biomedical applications

Abstract

Magnesium and its alloy has become the most promising candidate to substitute the conventional biomaterial such as stainless steel, cobalt chromium and titanium nowadays. Its tremendous mechanical properties such as lightweight, high availability and low cost have made this metal and its alloy gained a wide popularity in degradable implants applications for biomedical field. AZ series alloy which consist of aluminium and zinc with magnesium as their base are the most investigated for biomedical applications among the magnesium alloy. For this type of magnesium alloy series, aluminium content plays a crucial part in differentiating the the properties Mg-based alloy for biomedical applications. Thus, this project picks up pure Mg, AZ31 and AZ91 magnesium alloy and the effect of aluminium content has been investigated in simulated body fluid (SBF) solution. The bone bonding ability of a material is often evaluated by examining the ability of apatite to form on its surface in a SBF with ion concentrations nearly equal to those of human blood plasma. Surface morphologies also showed the formation of more pits on pure Mg and AZ91 Mg alloy compared with AZ31 Mg alloy. The pits might influence the ability of the Mg-based alloy to withstand the corrosive agent that will attack the alloy while being immersed in SBF. The phases on the corroded sample surfaces were examined by X-ray diffraction (XRD) method and scanning electron microscopy (SEM) and found that the corrosion products which were deposited on the surfaces provided protection against the chloride ions which was indicated by the decreased corrosion rates as immersion time was increased. Increasing of the immersion time may give a better result in bioactivity behaviour of the Mg-based alloy.