Developments of Free Cutting Titanium Alloys for Dental CAD/CAM

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Free cutting titanium alloys for dental CAD/CAM, which have been dispersed fine brittle phase such as metastable α', α'', ω or intermetallic compound, were developed. β stabilizing elements of gold, silver, copper, niobium and hafnium were selected as alloying elements of titanium. Gold, silver and copper make eutectoid among titanium and these titanium compounds. Niobium or hafnium form complete solid solution with titanium. Machinability, mechanical properties and corrosion resistances of these titanium alloys were investigated.Ti-30%Nb alloy showed significantly higher grinding rate at lower grinding speeds. Ti-20%Ag alloy and Ti-5%Cu alloys showed also significantly higher grinding rate at higher grinding speeds. Ti-30%Nb alloy, Ti-20%Ag alloy and Ti-5%Cu alloy had significantly higher tensile strength and Vickers hardness with reasonable elongations. Ti-30%Nb alloy may has good corrosion resistance because both of titanium and niobium have excellent corrosion resistance. Ti-20%Ag … More alloy and Ti-5%Cu alloy showed good corrosion resistance from the anodic porlaization curves and dissolution of ions equivalent to that of titanium. Then, machinability and mechanical properties of Ti-24%Nb-1%Cu alloy, Ti-18%Nb-2%Cu alloy and Ti-6%Nb-4%Cu alloy, which were mixed with Ti-5%Cu alloy and Ti-30%Nb alloy were investigated. Tensile strength of the experimental ternary titanium alloys were 700-860 MPa and significantly higher than those of CP titanium, Ti-5%Cu alloy and T-30%Nb alloy with about 4% elongation. The hardness of the experimental ternary titanium alloys were Hv 260-330. The grindability of Ti-6%Nb-4%Cu alloy increased with increasing grinding speed and became significantly larger than that of CP titanium above the grinding speed of 1250 m・min^<-1>. The garindability of Ti-18%Nb-2%Cu alloy was significantly higher than that of CP titanium at low grinding speed and became four times larger than that of CP titanium. The experimental Ti-Nb-Cu alloys may have good grindability and mechanical properties as CAD/CAM alloys for dental use. Less