| 摘要 |
PROBLEM TO BE SOLVED: To provide a titanium alloy cast material having improved fatigue strength characteristics without aggravating ultrasonic flaw detectability.SOLUTION: Within the provided &bgr;-forged titanium alloy cast material 1, the area ratio of non-flat grains prevailing as ex-&bgr; grains 2 having an aspect ratio of 3 or below, a diameter of 20 μm or above along the forging direction, and an α-phase occupant ratio of 80% or above within a crystal grain boundary 3 is below 10%. The area ratio of flat grains prevailing as ex-&bgr; grains 2 having an aspect ratio higher than 3, a diameter of 20 μm or above and 700 μm or below along the forging direction, and an α-phase occupant ratio of 80% or above within the crystal grain boundary 3 is 85% or above. The average orientation difference of α-phase crystals deposited on the crystal grain boundary of the flat grains is 6° or higher. |
