【摘要】 通过对不同应力幅度下高纯钛的反复弯曲疲劳的研究，发现在较低应力幅度下（～±１００ＭＰａ），材料表现出循环软化，伴随表面滑移带数量的增加、发达的滑移带挤出片的出现。疲劳裂纹萌生主要与滑移带相关，在挤出物内存在两类疲劳损伤形式：沿滑移带的孔洞和与滑移带垂直的微裂纹。在较高应力幅度下（～±２００ＭＰａ），则表现为硬化，次滑移及晶界附近多个滑移系同时起动，有大的形变孪晶出现。裂纹于滑移带、李晶界和晶界结点萌生。断口特征复杂，但与表面变形特征有对应关系。ＴＥＭ亚结构分析表明，随应力幅度的提高，位错组态分别为散乱分布于滑移面的偶极子、位错束带和位错胞。李晶内存在复杂的精细结构，而且有堆垛层错出现。更多还原

【Abstract】 Alternating bending fatigue behavior of high purity titanium has been studied at a series of stress amplitudes. At the low stress amplitude (±100 MPa ),cyclic softening occurred after a certain number of cycles. Surface exam mation revealed that the softening was accompanied by an increase of slip bands and the formation of well-defined slip band extrusions.Two distinct modes of fatigue damage were identified in the extrusion ribbons:cavities along the slip bands and microcracks perpendicular to the slip bands. At the high stress level(± 200M Pa ),cyclic hardening occurred and was accompanied by the activation of secondary slip system and huge cyclic twins. Slip bands were the most favorite sites for fatigue crack initiation at all stress levels. Cracks initiated along the twin/matrix interfaces and grain boundaries were also observed. Highly irregular appearances of fracture surfaces have some relations with the surface deformation features. TEM analysis indicated that the substructure were identified as dislocation dipoles, dislocation bundles and disloca tion cells when the stress amplitude increased. Fine structures in the cyclic twins were complex and stacking faults were observed in the twins.更多还原