Fabrication of biocompatible Mg-based nano composites by using friction stir alloying

In the present research, friction stir processing technique was performed to ameliorate the MB3 magnesium alloy surface through grain reduction and integration of bio-ceramic Nano particles. The friction stir processing was carried out at 1140 rpm and 100 mm/min by using a tapered tool pin profile. The incorporated bio-ceramic Nano particles are hydroxyapatite, tri-calcium phosphate and aluminum oxide. The results revealed that all processed samples have finer grain structure than that of the magnesium matrix, which caused an increase in the average microhardness values in the stirred zone. Furthermore, the tensile properties revealed an enhancement in elongation of all processed samples with deterioration in both ultimate tensile and yield strength values. On the other hand, the electrochemical impedance spectroscopy results exposed larger capacitive radius of all samples compared with the base material which reflects the improvement in the corrosion resistance. Accordingly, the potentiodynamic polarization results of all manufactured samples showed better bio-corrosion resistance in simulated body fluid than that of the base material, where the best corrosion resistance was achieved by magnesium-hydroxyapatite composite. The results obtained from the immersion test results manifested lower corrosion rates of all processed samples; where the friction stir processed and magnesium-hydroxyapatite samples corrosion rates were about 66% and 31% respectively of the base material. The corroded surfaces of all samples contained filiform and pitting corrosions after 72 h of immersion in simulated body fluid.