TB6钛合金疲劳及裂纹扩展性能研究

本文对TB6钛合金锻件弦向和径向两种取样方向分别进行了室温和200℃下旋转弯曲高周疲劳、轴向低周疲劳和疲劳裂纹扩展性能试验研究。试验结果表明，弦向（C）和径向（R）两种取样方向对该合金锻件的旋转弯曲高周疲劳、轴向低周疲劳性能和疲劳裂纹扩展性能没有影响；温度升高可加速该合金锻件的疲劳裂纹萌生，但在裂纹扩展阶段，该合金高温下的韧性优势与屈服强度降低的劣势平衡的结果使其在室温～200℃温度范围内的疲劳性能基本不受温度的影响；在10—20mm的厚度范围内，厚度对该合金的疲劳裂纹扩展性能没有影响；在3．5％NaCl盐雾环境中。腐蚀介质对TB6钛合金的疲劳裂纹扩展速率在初始阶段有迟滞作用，但在应力强度因子范围大于14MPa m后有加速作用。

Study on Fatigue Property and Crack Growth Behavior of TB6 Titanium Alloy

The tests about rotary bending high-cycle fatigue, axial low-cycle fatigue and fatigue crack growth of TB6 titanium alloy were carried out at room temperature and 200℃ in the chord and radial directions. The results show that the rotary bending highcycle fatigue, axial low-cycle fatigue and fatigue crack growth properties of TB6 titanium alloy are not affected by the direction of the specimen. The elevated temperature can accelerate the initiation of the fatigue cracks, but at the crack growth stage, the variation of temperature from room temperature to 200℃ has no influence on the fatigue properties because of the co-effect of higher toughness and lower yield strength at high temperature. In addition, it is found that the fatigue crack growth property is not affected by the variation of the thickness of the specimen if the thickness is in the range from10 to 20mm. Fatigue tests were also carfled out in air and corrosion medium environment respectively. The results show that corrosion medium retarded the growth of the cracks at the early stage in the environment of 3.5% NaCl, but then it accelerated the growth of the fatigue cracks when the stress intensity factor was more than 14MPa m.