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采用旋转弯曲和超声疲劳实验分别测试了全等轴和等轴双态组织Ti-6Al-4V合金的高周和超高周疲劳性能,并用SEM观察了疲劳断口特征.结果表明:2种组织Ti-6Al-4V合金的高周和超高周疲劳行为相似,不同应力比下,其S-N曲线均表现出单线形或双线形的形式;存在滑移机制和解理机制2种疲劳破坏机制.随应力比增加,2种组织Ti-6Al-4V合金的高周和超高周疲劳破坏机制均从滑移机制向解理机制转变.基于疲劳寿命和疲劳强度建立模型分析了应力比对2种机制之间竞争行为的影响,模型预测结果与实验结果趋势吻合.
The high-cycle and ultra-high-cycle fatigue properties of Ti-6Al-4V alloy with isometric and equiaxed Ti-6Al-4V alloys were measured by rotational bending and ultrasonic fatigue tests, respectively. The fatigue fracture characteristics were observed by SEM. -4V alloy have similar high-cycle and ultrahigh-cycle fatigue behaviors, and all SN curves show single or double line shape under different stress ratios. There are two kinds of fatigue failure mechanisms of slip and cleavage mechanism. With the increase of stress ratio, The high-cycle and ultra-high-cycle fatigue failure mechanisms of the two kinds of Ti-6Al-4V alloys both changed from the slip mechanism to the cleavage mechanism.The model was established based on the fatigue life and the fatigue strength to analyze the effect of stress ratio on the competition behavior between the two mechanisms , The predicted results of the model are in good agreement with the experimental results.