α+β钛合金旋转弯曲疲劳性能各向异性的研究

Anisotropy of Rotating Bending Fatigue Properties of α+β Titanium Alloy

摘要:

研究了微观组织和织构对β锻造的α + β两相钛合金镦饼旋转弯曲疲劳性能各向异性的影响,利用OM、SEM、XRD和EBSD等手段表征了镦饼不同方向及不同厚度处的显微组织以及织构分布,分析了微观组织和织构对旋转弯曲疲劳性能各向异性的影响。结果表明,合金经β锻造后,呈网篮组织特征,原始β晶粒压扁拉长,且晶界处存在再结晶晶粒；镦饼形成β相<100>//轴向的丝织构和α相<0001>//径向的织构。径向试样旋转弯曲疲劳强度优于轴向试样,这与镦饼的原始β晶粒形态和织构类型均有关,原始β晶粒的排布导致不同取向裂纹萌生的难易程度和裂纹扩展路径曲折程度不同；此外,α相和β相织构也造成不同取向在循环加载时滑移系开动难易程度不同造成疲劳强度产生差异。

Abstract:

The effects of microstructure and texture on the rotating-bending fatigue anisotropy of an α+β two-phase titanium alloy by β forging was investigated. The microstructure and texture distribution of forged billet in different directions and thicknesses were characterized by OM, SEM, XRD and EBSD, and the effects of microstructure and texture on the rotating-bending fatigue anisotropy were analyzed. The results show that after β forging, the alloy has the characteristics of basket-weave microstructure, the prior β grains are flattened and elongated, and there are recrystallized grains at the grain boundary. The texture of β-phase <100>// axial direction and α-phase <0001>// radial direction formed by forged billet after β forging. The rotarting-bending fatigue strength of radial direction samples is better than that of axial direction samples, which are related to the morphology and texture type of the prior β grains of forged billet. The arrangement of the prior β grains leads to different initiation of cracks and different tortuous degree of crack growth path. In addition, the α and β textures also cause the fatigue strength differences due to the difficulty of slip systems activation of samples in different directions under cyclic loading.