A turbine engine blade alloy (Ti-8Al-1Mo-1V) under different heat treatment conditions was employed to conduct ultrasonic fatigue tests to investigate the influence of the colony content of bimodal titanium alloys on the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) behavior. As a result, the increase in the content of colonies or the decrease in the content of primary α grains (α_p) can be achieved by a double-annealed treatment below the α + β to β transformation temperature. A higher colony content will result in a higher HCF and VHCF properties. The crack initiation life has a lower sensitivity to the microstructure change in the α_p/colony content than the fatigue crack growth life. With the fatigue life increasing from the HCF regime to the VHCF regime, the impact of the microstructure evolution on fatigue resistances gradually decreases. Irreversibly, slips mainly along the maximum shearing stress direction make the plastic strain accumulate within some favorably oriented α_p grains and further cause the nucleation of fatigue micro-cracks. The formation of the fine granular area is attributed to the comprehensive effects of the vacuum-enhanced plasticity and the numerous cyclic pressing.

中文翻译：

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α+β群体积含量对钛合金超高周疲劳行为的影响

采用不同热处理条件下的涡轮发动机叶片合金（Ti-8Al-1Mo-1V）进行超声疲劳试验，研究双峰钛合金的菌落含量对高周疲劳（HCF）和超高周疲劳的影响。疲劳 (VHCF) 行为。因此，通过在α + β 到β 转变温度以下进行二次退火处理，可以实现集落含量的增加或初生α 晶粒(α _p )含量的减少。更高的菌落含量将导致更高的 HCF 和 VHCF 特性。裂纹萌生寿命对α _p的微观结构变化的敏感性较低/菌落含量大于疲劳裂纹扩展寿命。随着疲劳寿命从 HCF 状态到 VHCF 状态的增加，微观结构演变对疲劳抗力的影响逐渐减小。不可逆转的是，主要沿最大剪切应力方向的滑移使塑性应变在一些有利取向的α _p晶粒内积累，进一步导致疲劳微裂纹的形核。细粒区的形成是真空增强塑性和多次循环压制的综合作用。