| Titanium and its alloys have been used as implant materials in dental and orthopaedic applications owing to their excellent mechanical properties and corrosion resistance. However, the lack of bioactivity remains a problem. Magnesium has potential to be biomaterial because of its degradability in vivo environment and good bioactivity, the unfortunate complication is that magnesium corrodes too quickly in human bodies. To combinate the respective advantages of titanium and magnesium, a new Ti-Mg alloy for bone tissue repair and replacement is prepared in this work.In this investigation, the Ti powder and the Mg powder in different mass ratios were mechanical alloyed to produce Ti-xMg (x=5,10,15wt.%) alloy powders, which were then sintered by Spark Plasma Sintering (SPS) to fabricate Ti-Mg alloys. Properties and micro structure of those powders and alloys were investigated by means of laser particle sizing, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma Atom Emission Spectrometer (ICP-AES) and mechanical testing. Electrochemical corrosion behavior and bioactivity of the alloys were evaluated by simulating body fluid (SBF) in vitro and electrochemical test technique. The main results can be summarized as follows:Based on experiments, the optimum parameters to prepare Ti-Mg alloy powders were obtained:milling speed of240r/min, ball to powder ratio of10:1, milling time of30h. During the milling process, Mg dissolved in Ti gradually with increasing milling time. With increasing Mg content the particle size of Ti-Mg powder decreased.Ti-Mg alloys were fabricated by SPS under the condition of10KN and800using an SPS apparatus. XRD analysis of Ti-5Mg alloy showed that the alloy consist of titanium, titanium monoxide and magnesium oxide, meanwhile Ti-lOMg alloy and Ti-15Mg alloy consist of titanium, titanium monoxide, magnesium and magnesium oxide. The microstructure of Ti-Mg alloys was nearly compact, and a mount of pores left by sintering process and Mg vaporizing existed. The relative density of Ti-Mg alloys were99.68%,99.44%and93.49%respectively, which decreased with the amount of Mg added. According to the calculation results of Ti-Mg alloys, Ti-5Mg alloy did not lose Mg during the sintering process, while Ti-10Mg and Ti-15Mg alloy lost3.2wt.%and5.77wt.%Mg.By employing mechanical properties tests, the results showed that Ti-5Mg and Ti-lOMg alloy had hardness of HV469.28and HV406.69, compressive strength of1690.89MPa and1671.72MPa respectively, meanwhile, Ti-15Mg alloy had hardness of HV360.17and compressive strength of1373.06MPa. The hardness and compressive strength of Ti-Mg alloys decreased with increasing Mg content.The results of in vitro tests showed that the calcium phosphate deposits in all three Ti-Mg alloy. As the Mg content increases, precipitates of the calcium phosphate increased. The analysis revealed that Mg separates out from samples during immersed in SBF, which results in the enrichment of Ca and P in the electrolyte space charge facing the surface. The trend is that the supersaturation level of calcium phosphate precipitation preferentially increased in the region adjacent the surface. The addition of Mg improves the bioactivity of titanium. The electrochemical test showed that Ti-Mg alloys stay stable in corrosion process. The corrosion potential of Ti-Mg alloys decreases and the corrosion density Ti-Mg alloys increases with the increasing Mg content. The corrosion resistance performance of Ti-Mg alloys become worse with the increasing Mg content on the basis of the high electrochemical activity of magnesium. |
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