Duality of the fatigue behavior and failure mechanism in notched specimens of Ti-7Mo-3Nb-3Cr-3Al alloy

• 作者: Zhihong Wu Hongchao Kou Nana Chen Mengqi Zhang Ke Hua Jiangkun Fan Bin Tang Jinshan Li
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2020,（15）
• 页码范围: 204-214
• 页数: 11页
• 语种: 英文

摘要

An interesting phenomenon of dual S-N fatigue behavior is investigated in a metastable β titanium alloy,Ti-7Mo-3Nb-3Cr-3Al notched cylindrical specimens with an elastic stress concentration factor of Kt =3.Fractographic studies revealed all specimens,and irrespective of lifetime,failed from the specimen surface because of stress concentration occurs at the notch root.Typically,the short-life-distribution is usually associated with surface-failure-without-facets and the long-life-distribution generally occurs due to surface-failure-with-facets.This competing failure leads to increasing the variability in fatigue lifetime and further facilitates the difficulty in prediction of fatigue lifetime.Crack-initiation area characterization was conducted by using mechanical grinding,focused ion beam milling and subsequent electron back-scattered diffraction (EBSD) analysis of the 2D section across faceted grains.Results show that the αp particles (especially the elongated αp particles) well-oriented for basal slip activation is a preferential fatigue-critical microstructural configuration.Additionally,the β+αs matrix has a higher KAM value than the αp particles in fatigued microstructures and significant dislocation activity in the form of dislocation tangles is observed in αp boundaries.