Effect of grain refinement on biodegradation and biomineralization of low calcium containing Mg–Ca alloy

Abstract

The biodegradability and mechanical properties of magnesium make it suitable for temporary implant applications. However, its degradation rate in the physiological environment needs to be controlled. The effect of grain refinement on the degradation rate in the physiological environment is investigated in this work. Samples with different grain size were developed by heat treatment and friction stir processing (FSP) techniques. Potentiodynamic polarization test in NaCl solution and immersion test in supersaturated simulated body fluid (SSBF) were conducted to evaluate the degradation resistance of the samples. The effect of grain refinement on biomineralization was also studied by analysing the surface morphology and composition of the immersion tested samples using SEM and EDAX. It is noted that the grain refinement improves the degradation resistance as well as biomineralization. The enhancement in the biomineralization resulted in the development of a calcium phosphate layer on the surface during the immersion test, which in turn reduced the degradation rate further. Hence grain refinement can be used as an effective metallurgical modification technique to tailor the degradation rate of Mg–Ca alloys in the physiological environment.

Keywords

• Mg alloys
• biodegradation
• biomineralization
• grain refinement
• friction stir processing