Microhardness and biological behavior of AZ91D-nHAp surface composite for bio-implants

In the present research work, friction stir processing (FSP) has been adopted for the fabri­cation of nano-hydroxyapatite (nHAP) reinforced AZ91-D Mg-alloy matrix surface com­posite (NMMSC). The NMMSC was developed to replace the conventional bio-implants materials for short-term usage. The NMMSC has been prepared by adding nHAp rein­forcement in 12.5 % volumetric proportion in the AZ91-D alloy using the grooving technique followed by FSP. The FSP parameters were selected, such as the tool rotation of 1000 rpm, 50 mm/min transverse speed, and 5 multi-passes. The base alloy, normal FSPed, and fabricated NMMSC were characterized to study their micro-hardness values and biological performances. Improvement in microhardness value in the developed composites was observed due to the smaller grain size as a result of the dynamic recrystal­lization phenomenon. The antibacterial properties of FSPed and NMMSC specimens tested against Staphylococcus aureus, Candida albicans, and Aspergillus fumigatus were found to be superior as compared to the PM. The cytotoxicity of the FSPed & NMMSC specimens expressed as cell viability using MTT assay shows negligible toxicity as compared to PM and the cell viability was insignificantly decreased as the incubation period was extended. The microhardness and biological performance of NMMSC have been improved due to the grain refinement by FSP and the presence of nHAp reinforcement in the material.