Construction of Ti-Nb-Ti2Cu pseudo-ternary phase diagram

Mechanical Properties of Ti-Nb-Cu Alloys for Dental Machining Applications

Titanium has excellent biocompatibility and good corrosion resistance and is extensively used in dental implants and denture bases. However, pure titanium lacks the strength for use in dental prostheses that require relatively high strength. We developed 15 different types of Ti-Nb-Cu alloys and investigated their alloy phases and mechanical properties, including tensile and yield strength, elongation after fracture, and Vickers hardness. The alloy phases of Ti-8%Nb-2%Cu and Ti-13%Nb-2%Cu were α + β, while those of Ti-5%Nb-5%Cu and Ti-10%Nb-5%Cu were α + Ti₂Cu. The tensile strength and hardness of these alloys were significantly higher than those of titanium; however, their elongation was less. In particular, the yield strength of these alloys was more than twice that of titanium. These differences in mechanical properties are attributable to solid-solution strengthening and precipitation strengthening. Other compositions with an alloy phase of α + β + Ti₂Cu or β + Ti₂Cu had high hardness but not high strength. These results suggest that the Ti-8%Nb-2%Cu, Ti-5%Nb-5%Cu, Ti-13%Nb-2%Cu, and Ti-10%Nb-5%Cu alloys can be applied to dental prostheses, which are subject to very high forces from accessories such as long-span bridges, clasps, implant-retained superstructures, and narrow-diameter implants.

Grindability of Ti−Nb−Cu Alloys for Dental Machining Applications

We developed high-strength Ti−Nb−Cu alloys and investigated their grindability. The grindability of each alloy was evaluated based on the volume of metal removed per minute (grinding rate) and on the ratio of the metal volume removed to the volume of the wheel material lost (grinding ratio). The grinding rate of the Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and Ti-24%Nb-1%Cu alloys significantly exceeded that of unalloyed titanium at high, medium, and low grinding speeds, respectively. Additionally, the Ti-6%Nb-4%Cu alloy exhibited an excellent grinding ratio. Generally, materials with high strength and hardness frequently exhibit poor machinability; however, the Ti−Nb−Cu alloys developed in our study presented favorable grindability characteristics and, therefore, demonstrated good potential for application as dental titanium alloys that can be subjected to computer-aided design/manufacturing processes.