Influence of heat treatment cooling mediums on the degradation property of biodegradable Zn-3Mg alloy

Abstract

Recently, Zn-based alloys were introduced as alternative biodegradable metals to the well-studied Mg and Fe based alloys for temporary implants. In this work, Zn-3Mg alloy was developed using a conventional casting method followed by heat treatment with different cooling media. As-cast samples were heat treated at 370 o C for 10 hours then cooled in open air, water bath and inside furnace environments. The microstructure of as-cast alloy was characterized under optical microscope and phase analysis was evaluated using X-ray diffraction (XRD) technique. Potentiodynamic polarization tests were carried out on the heat treated samples for evaluating the degradation rate. It was observed that as-cast Zn-3Mg alloy consists of star-like-shape of primary Zn-rich dendrites which are segregated in the eutectic mixture of Mg 2 Zn 11 phase. The segregation of these dendrites has been significantly reduced under water bath cooled treatment as compared to open air and inside furnace cooling. It is also found that the microstructure of the water cooled samples is more homogenous with less porosity than the as-cast, air or furnace cooled samples. The water cooled sample exhibits better degradation resistance for at least 2 folds than other treatments. © (2014) Trans Tech Publications, Switzerland.