TiAl 합금에서 prestrain에 의한 primary 크리프 영역에서의 변형기구 변화

초록

Creep deformation behaviors in lamella TiAl alloy have been investigated. We developed a new method, applying a small amount of prestrain at high temperature with slow tensile rate, in order to enhance primary creep resistance of these alloys. This method is founded on creep deformation mechanism which has been suggested by authors of present investigation . Prestrained specimens had much lower density of initial dislocations than that of non-prestrained one. In addition, the prestrained specimen, deformed less than 0.2% plastic strain, showed the improved primary creep resistance in temperature range from 775℃ to 900℃ at 150㎫ condition compared with non-prestrained specimen. Activation energies of the prestrained specimen within the primary creep regime were high as much as that of steady state. These results imply that the creep deformation mechanism of the prestrained specimen within the primary regime shift from climb of the initial dislocations to phase transformation of α2 to γ phase.