Characterization and micro-machinability of magnesium alloys fabricated through powder metallurgy method

In this thesis study, production and characterization of Mg alloy which can be used in biomedical applications has been realized. In study, Mg5Sn-xZn (x = 0, 1, 2, 3, 4 and 5 wt%) samples were produced by using the hot pressing method which is a powder metallurgy (P/M) technique. Microstructure investigations of each alloy were carried out and mechanical and corrosion properties were determined. However, cell viability analysis was performed to determine the effect of toxicity against human neuron cells. As a result of corrosion, biocompatibility and mechanical tests, micro-milling tests were carried out to determine the micro-machinability parameters of the alloy sample with optimum properties. The results showed that it is possible to produce Mg5Sn-xZn alloy by hot pressing method. From the SEM/EDS results of the specimen surfaces, it was observed that a homogeneous microstructure could be obtained, and the formed secondary phases were uniformly distributed at the grain boundaries. It was determined that the corrosion resistance increased with increasing Zn ratios. After the corrosion tests, it was determined that apatite structures were formed in the form of protective films on the specimen surface. The highest corrosion resistance was obtained from TZ54 alloy, in which the apatite structures formed intensively; however, an increase in the amount of Zn was found to enhance the mechanical properties with the highest mechanical properties being obtained from TZ55 alloy. The addition of Zn to the alloys had no toxic effects on SH-SY5Y cells in terms of biocompatibility but was effective for cell growth. For the properties of corrosion and biocompatibility, the TZ54 sample provided optimum properties. For this purpose, micro milling experiments were carried out, considering different cutting parameters. In order to determine the appropriate cutting parameters, the cutting forces, surface quality and variation of burr width were investigated. The cutting forces obtained in micro milling of the TZ54 alloy are relatively small compared to other biomedical materials. In terms of both cutting forces and surface roughness, minimum chip thickness was determined to be approximately 7% of the tool edge radius. However, compared to alloys such as Ti6Al4V and AZ31, the formation of burrs is smaller. The burr width increases at feed rates lower than the minimum chip thickness. The predominant type of damage in the cutting tool is abrasive wear. Partial chip adhesion has also been observed. In view of tool life, surface roughness and burr formation, it is envisaged that the TZ54 alloy can be an easily machinable, alternative biomedical material.