| To determine the optimum thermochemical processing (TCP) methods, A Ti-6Al-4V alloy was hydrogenated with 60% hydrogen and 40% argon mixture gas at 760℃ and 830℃ for various times. After holding the hydrogenated Ti specimens at 760℃ and 830℃ for 30 minutes, they were pre-treated with various cooling rate for providing the nucleation sites for hydrides. And then they were aged at 500℃ for 2-10 hours for the formation of hydrides. Finally, Ti specimens were dehydrogenated at 700℃ and 830℃ for 2-30 hours to degas and refine microstructures via recrystallization. Specimens were tested with Instron machine to determine the mechanical properties. Also, the superplastic deformation tests were carried out at 840℃, 880℃ and 927℃ to measure the superplsticity of the specimens. As a result of TCP, Ti specimens exhibited fine equiaxed grains of 2㎛. Grain refinement with TCP induced the increase of mechanical properties and superplastic characteristics. |
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