Basic Study on the Superplastic forming of Dental Prostesis

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Ti-6Al-4V alloy can be deformed easily and enormously by small stress at superplastic temperature of 850ﾟC.This temperature is about half of the melting temperature of for casting. It was applied for fabricating a dental prosthesis as substitute for titanium casting prosthesis. The superplastic formability, mechanical properties and corrosion resistance of Ti-6Al-4V alloy was investigated. Ti-6Al-4V alloy denture base was fabricated by superplastic forming. Almost the same procedure as for dental casting was employed in producing the superplastic forming die. The fits of superplastic forming denture base was better than that of casting Co-Cr alloy denture casting. The tensile strength and yield strength were higher than those of Co-Cr alloy castings. Argon gas pressure bulgde test was employed to make clear the relations between the superplastic formability and the forming conditions. The results showed that the formability of 60 minute at 950 ﾟC, 8kg/cm^2 might be enough to fabricate a denture base.During the superplastic forming of denture base, diffusion bonding of pure titanium Titanium alloys and Co-Cr alloy to Ti-6Al-4V alloy was investigated. Pure titanium and Titanuim alloys were successfully bonded by using insert metals such as gold, palladium, Ag-Pd-Au alloy solder and gold alloy solder. The diffusion bonding superplastic denture base showed superior corrosion resistance.