Developing composites of ZE41 Mg alloy - naturally derived hydroxyapatite by friction stir processing: investigating in vitro degradation behavior

In the present study, ZE41 Mg alloy and fish bone derived hydroxyapatite (fHA) have been selected to develop fine grained surface composites by friction stir processing (FSP) targeted for degradable implant applications. Surface composite was successfully developed at process parameters of 1400 rpm with 25 mm/min feed. Microstructural observations exhibited grain refinement from a starting size of 110 µm to 3 µm. Increased hardness was observed for the composite due to the fine grain size and the presence of fHA powder. X-ray diffraction (XRD) studies showed significant orientation change in the grains after FSP. Degradation behavior assessed by immersing the composites in Ringer’s solution indicated uniform corrosion compared with ZE41 Mg alloy. From the potentiodynamic polarization tests, marginally decreased corrosion rate was observed for the composite however the deference is insignificant. Hence from the results, it can be concluded that low cost novel composites of ZE41-fHA can be produced without significantly altering the corrosion rate. The introduced fHA enhances biomineralization and promotes rapid healing rate in the orthopedic implants applications.