||Titanium alloy has excellent mechanical properties, thermal properties and biocompatibility, it has been applied as aerospace materials and biomaterials. According to the literature, Ti-Au alloy and Ti-Pd alloy can improve the mechanical and corrosion properties. The study of Ti-Au-Pd ternary phase diagram could provide the information of titanium alloy design.|
In this study, the diffusion couple technique applied to determine the diffusion path that will provide the information of two-phase equilibrium and three-phase equilibrium. Then, the traditional alloy equilibrium technique applied to verify the three-phase equilibrium and those regions that the diffusion paths did not through it. This could the cost of gold and palladium. The diffusion couples and alloy specimens are sealed in a vacuum quartz tube and annealed at 800℃ for one day and 21 days, respectively. The diffusion couple and alloy samples were examined by electronic-probe- micro-analyzer (EPMA) to determine the equilibrium phase composition.
There are eight three-phase equilibrium as, (1)αTi-βTi-Ti3(Au,Pd)、(2)Ti3(Au,Pd)-Ti2Pd-Ti(Au,Pd)、(3)Ti(Au,Pd)-Ti2Pd3-Ti(Au,Pd)2、(4)Ti2Pd3-Ti(Au,Pd)2-Ti3Pd5、(5)Ti(Au,Pd)2-TiAu4-T、(6)Ti(Au,Pd)2-T-TiPd3、(7)TiAu4-T-(Au,Pd)、(8)T-(Au,Pd)-TiPd3 and twenty two-phase equilibrium determined in this study. There are three complete solid solution phases: Ti3Au-Ti3Pd, TiAu-TiPd and TiAu2-TiPd2. One ternary phase (Ti25Au25Pd50) was discovered with the composition range：22.3 at%~26.1 at% Ti、23.3 at%~32.4 at% Au、43.1 at%~58.0 at% Pd. The other determined solubility range are, 17.6 at% Au in Ti2Pd, 8.76 at% Au in Ti2Pd3, 10.0 at%Au in TiPd3 and 36.1 at% Pd in TiAu4.