생체재료용 Ti-Au 합금의 생체적합성 및 전기화학적 특성

Abstract

Recently, pure titanium has been widely used in dentistry and orthopedic surgery because of its high corrosion resistance and biocompatibility. The purpose of this study is to develop titanium-gold alloy with higher corrosion resistance, better biocompatibility and higher mechanical property than pure titanium. We designed titanium-gold alloys with gold contents ranging from zero to 5.0 at% in steps of 1.0 at%. The alloys were arc-melted, homogenized at 950?C for 72 hours, hot-rolled to 2 mm in thickness, and finally solution heat-treated at 950?C for 1 hour and quenched into water bath. Chemical compositions, microstructures, phases, harnesses, electrochemical properties and cytotoxicities were investigated. Alpha phase existed in the titanium-gold alloys with 1 at% Au, and Ti3Au precipitates as well as alpha and beta phases with more than 2 at% Au. Addition of gold to titanium decreased alpha to beta transformation temperature, that is, it stabilized the beta phase. The acicular phase got thinner and smaller and the hardness value got higher with increasing gold content. This increase of hardness was considered to be due to solid solution strengthening, coexistence of alpha and beta phases, martensitic transformation and precipitation hardening. In the electrochemical test, titanium-gold alloys had higher corrosion resistances than pure titanium and did not show pitting corrosion in artificial saliva. These results mean that gold addition to titanium can improve corrosion resistance because alloying addition of noble metal with low hydrogen over voltage increases the mixed potential of titanium-gold alloys. The cytotoxicities of titanium-gold alloys and titanium were none or slight and fibroblast cell viabilities to titanium-gold alloys were more than 92%. In summary, titanium-gold alloys had higher hardness and corrosion resistance than pure titanium and toxicities similar to pure titanium. Therefore, titanium-gold alloy can be used as good biomaterials in biomedical and dental fields.