| The effect of α phase precipitation on the tensile property and fatigue limit of -C type Ti-3Al-8V-6Cr-4Mo-4Zr alloy has been investigated. For the control of α phase precipitates morphology, it has been carried out aging treatments in the temperature range of 430℃ to 580℃ to the annealed or annealed and cold drawn specimens. The shape, size and distribution of α phase precipitates were changed with the annealing or aging temperature. In case of aged at 430℃ to the annealed and cold drawn specimen, a lot of fine α phase precipitates have been distributed homogeniously all over the matrix, and it has shown the highest tensile strength of 1,543㎫. However, the highest fatigue limit of 705㎫ and the highest endurance ratio of 0.552 have been obtained from the specimens that has been aged at 530℃. In this case, the fine α phases have been precipitated by a separation reaction of β→β+α. On the other hand, in the specimens annealed at 800℃ or 900℃, namely, near or above the β transus, the grain growth has been notable. The α phases were gradually precipitated along the grain boundaries as the aging temperature increased. In this study, the orientation relationship between α phase precipitates and matrix was identified as (110)_β//(11￣01)_α and [001]_β//[011￣1]_α Moreover, the most of α phase precipitates have shown the type 1 α(obeying the Burgers orientation relation). |
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