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Effect of stress ratio on long life fatigue behavior of Ti-Al alloy under flexural loading


A new ultrasonic three-point bending fatigue test device was introduced to investigate fatigue life ranging up to 1010 cycles and associated fracture behavior of Ti-Al alloy. Tests were performed at a frequency of 20kHz with stress ratio R=0.5 and R=0.7 at ambient temperature in air. Three groups of specimens with different surface roughness were applied to investigate the effect of surface roughness on fatigue life. Furthermore, optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructure characteristic and fracture surface analysis. The S-N curves obtained show that fatigue failure occurs in the range of 105-1010 cycles, and the asymptote of S-N curve inclines slightly in very high cycle regime, but is not horizontal for R=0.5. Fatigue limit appears after 108 cycles for R=0.7. Surface roughness (the maximum roughness is no more than 3μm) has no influence on the fatigue properties in the high cycle regime. A detailed investigation on fatigue fracture surface shows that the Ti-Al alloy studied here is a binary alloy in the microstructure composed of α2-Ti3Al and γ-Ti-Al with fully lamellar microstructure. Fractography shows that fatigue failures are mostly initiated on the surface of specimens, also, in very high cycle regime, subsurface fatigue crack initiation can be found. Interlamellar fatigue crack initiation is predominant in the Ti-Al alloy with fully lamellar structure. Fatigue crack growth is mainly in transgranular mode.......

【作者名称】: XUE Hong-qian, TAO Hua, SHAO Ren-ping, B.CLAUDE
【作者单位】: School of Electromechanics, Northwestern Polytechnical University, Xi'an 710072, China, School of Electromechanics, Northwestern Polytechnical University, Xi'an 710072, China, School of Electromechanics, Northwestern Polytechnical University, Xi'an 710072, China, Department of Mechanical Engineering, CNAM/ITMA, 2 rue Conte, Paris 75003, France
【关 键 词】: bending fatigue, cycles fatigue, S-N curve, Ti-Al alloy, surface roughness
【期刊名称】: 中国有色金属学报(英文版)
【期刊论文数据库】: [DBS_Articles_01]
【期刊论文编号】: 105,449,981
【摘要长度】: 1,485
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