高強度ばね用チタン合金のねじり疲労強度に及ぼす金属組織の影響

抄録

The relationship of the aging treatment conditions, hardness, and torsional fatigue strength of the β type titanium alloy for the springs was examined, in addition observation of micro-structure change due to aging was conducted. As a result, the maximum hardness occurs at the aging treatment temperature of 450℃, while beyond this temperature it decreases. On the other hand, the torsional fatigue strength rises above 450℃, and reaches maximum at 540℃ aging treatment temperature. The notch sensitivity factor, β of the specimen for 600μm diameter-drilled hole is 1.29 at 480℃ and 1.24 at 540℃ aging treatment temperature, and the notch sensitivity factor, β of the specimen treated at 540℃ shows a lower value. Furthermore,the increases in the amount of α-phase precipitation due to aging increase the torsional fatigue, which becomes maximum when α-phase precipitation amount reaches 35%.