In vitro degradation behavior of grain refined WE43 magnesium alloy for biodegradable temporary implant applications

In the present work, grain-refined WE43 magnesium alloy was produced by friction stir processing to investigate the in vitro degradation behavior targeted for temporary bone implant applications. Friction stir processing resulted in significant grain refinement (from 46 +/- 4.2 mu m to 16.1 +/- 5.4 mu m) as observed from microstructural studies. Increased wettability was observed from the contact angle measurements in grain-refined WE43 alloy. The corrosion behavior of the base alloy and the grain refined alloy assessed by potentiodynamic polarization tests demonstrated the influence of the smaller grain size and decreased intermetallics on enhancing corrosion resistance. Immersion studies carried out in simulated body fluids for one week indicated a quick development of the protective magnesium hydroxide on the surface of grain-refined WE43 alloy compared with the base alloy. The deposition of the mineral phases from the immersed solution on the surface of the samples was studied by scanning electron microscopy and x-ray diffraction analysis to assess the effect of microstructure on the biomineralization. Promisingly, grain refined WE43 exhibited relatively excellent mineral deposition which further helped to control the degradation of the alloy. The weight loss measurements of the samples from the immersion tests were also in good agreement with the electrochemical test results. Hence, the results demonstrate the promising role of grain refinement by friction stir processing in tailoring WE43 magnesium alloy with better degradation behavior for temporary bone implant applications.