Effects of thermochemical treatment on mechanical properties of cast Ti-6Al-7Nb alloy for dental applications

Various thermochemical treatments were applied to cast Ti-6Al-7Nb in order to improve both its strength and elongation to meet the requirements for strength and elongation values in dental applications. The tensile properties of cast Ti-6Al-7Nb alloy with Various thermochemical processings were investigated with relating to microstructures comparing with the case of cast Ti-6Al-4V alloy. Grain diameter of alpha phases in A treatment where hydrogenation at 1023 K far 3.6 ks followed by air cooling and solutionizing at 1103 K for 3.6 ks followed by water quenching is carried out, and then dehydrogenation at 973 K for 54 ks followed by furnace cooling is carried out, B treatment where solutionizing at 1113 K for 3.6 ks followed by air cooling is carried out after A treatment, and E treatment where hydrogenation followed by aging treatment at 863 K for 7.2 ks after solution treatment is carried out, and then dehydrogenation is carried out are less than 3 mum in both cast alloys. Tensile strength of every thermochemical processed both cast alloys is greater than that in both as received cast alloys. Plastic deformability of beta phases in both cast alloys conducted with B treatment, and C treatment where solutionizing at 1198 K for 3.6 ks followed by water quenching is carried out after A treatment is improved according to their beta phase stability and volume fraction changed by heat treatments after A treatment. Cast Ti-6Al-7Nb alloy conducted with B and C treatments, and D treatment where heat treatment for spheroidization of alpha phase is carried out after A treatment and cast Ti-6Al-4V alloy conducted with B and C treatments show good balance between strength and ductility.