Ti60钛合金室温保载疲劳性能及断裂行为

Dwell fatigue property and fracture behaviour of Ti60 titanium alloy at room temperature

研究高峰值应力条件下Ti60钛合金双态组织和片层组织的低周疲劳与保载疲劳性能,利用金相显微镜(OM)、扫描电子显微镜(SEM)和电子背散射衍射(EBSD)等观察和分析Ti60钛合金的显微组织与疲劳断裂行为。结果表明:显微组织对低周疲劳性能影响不大,但显著影响保载疲劳性能,双态组织保载疲劳敏感性大于片层组织;保载情况下,疲劳寿命显著下降;随峰值应力的提高,疲劳寿命下降,保载疲劳敏感性增加;相同循环周次内,保载疲劳塑性应变累积大于低周疲劳,双态组织的塑性应变累积大于片层组织;低周疲劳裂纹萌生于试样表面,为单裂纹源,而保载疲劳裂纹为内部多源萌生;断口表面均存在准解理小平面,双态组织断口准解理小平面密度大于片层组织。

The low cycle fatigue (LCF) property and low cycle dwell fatigue (LCDF) property of bimodal structure and lamellar structure for Ti60 titanium alloy under high peak stress were studied by means of optical microscope (OM),scanning electron microscope (SEM) and electron backscatter diffraction (EBSD).The results show that microstructure has little effect on LCF property,while significantly influences LCDF property.The dwell fatigue sensitivity of bimodal structure is higher than that of lamellar structure.Under dwell loading condition,the fatigue life decreases remarkably.The fatigue life decreases with the increase of the peak stress,while the dwell fatigue sensitivity increases.Within the same cycle,plastic strain accumulation of LCDF is greater than that of LCF,and the plastic strain accumulation of bimodal structure is more than that of lamellar structure.The LCF crack initiates at the specimen surface with single source,while LCDF crack originates inside of specimen with multiple sources.There are quasi-cleavage facets on the fracture surface.The density of facets for bimodal structure is higher than that of lamellar structure.