산소와 철이 CP-Ti의 고온 변형 거동에 미치는 효과

Abstract

Effect of oxygen and iron on the high temperature deformation behaviors of CP-Ti was studied at temperatures from 750 ℃ to 950 ℃ using compression test at various strain rates from 0.001s^(-1) to 10s^(-1). High temperature deformation efficiencies and flow instability conditions were, in particular, evaluated from their high temperature flow curves. The work hardening rates were always higher in the grade 1 than in the grade 4 CP-Ti. This was mainly attributed to the difference in the range of α+β two-phase field arising from the different Fe content. The optimum working condition was estimated to be the strain rate of 10s^(-1) at 850℃ and to be the strain rate of 10s^(-1) at 900℃ for grade 1 and grade 4 CP-Ti, respectively. The dynamic recrystallization mechanism was believed to be mainly responsible for the high deformation efficiency for both grades. The increase of oxygen content shifted the condition for the high deformation efficiency toward a higher temperature or lower strain rate condition, in a good agreement with the theoretical expectation for the shift direction of the condition for dynamic recrystallization. At the intermediate strain rates and at about 900℃, power dissipation efficiencies were very low in both specimens. This was believed to be closely related to the occurrence of α→β transformation during deformation.