表面机械研磨工业纯锆的疲劳性能研究

Fatigue Property of Commercial Pure Zirconium Subjected to Surface Nanocrystallization

采用表面机械研磨工艺对工业纯锆进行处理,利用四点弯曲疲劳试验对试样的疲劳性能进行研究,并利用透射电子显微镜(TEM)和光学显微镜(OM)对试样的微观组织进行观察,利用纳米压痕仪测试处理试样从表层到基体的硬度分布,采用X射线衍射(XRD)方法分析表层晶粒尺寸、微观畸变以及残余应力分布特征。结果表明:经表面机械研磨处理工业纯锆的疲劳极限为195 MPa,而原始试样的疲劳极限为159MPa,表面机械研磨处理使工业纯锆的疲劳极限提高了23%,疲劳性能的改善可归因于表面机械研磨引入的纳米化表层、加工硬化以及残余压应力。本文进一步研究发现,应力幅大于270 MPa,表面机械研磨处理试样的疲劳寿命低于原始试样;应力幅低于270 MPa,表面机械研磨处理试样的疲劳性能比原始试样优异。

Commercial pure zirconium was processed by means of surface mechanical attrition treatment（ SMAT）,and the fatigue property of the sample was investigated using four-point bend fatigue test. Microstructure observation was carried out using transmission electron microscope（ TEM） and optical microscope（ OM）. Nano-indentation test was conducted to measure the micro-hardness variation from surface layer to matrix. X-ray diffraction（ XRD） method was used to evaluate the crystallite size and micro-strain of the treated surface layer and the in-depth residual stress. The results indicated that the fatigue limit of SMAT sample was 195 MPa,the fatigue limit of as-received sample was 159 MPa,and the fatigue limit could be increased by 23%,which could be attributed to the nanostructured surface layer,the work hardening and the compressive residual stress induced by the SMAT process. In addition,the fatigue life of SMAT samples was much less than that of as-received sample,of which the stress amplitude was greater than 270 MPa,and when it was less than 270 MPa,the fatigue property was superior to that of as-received sample.