激光增材制造体育器材用TC4钛合金疲劳裂纹扩展行为研究

Fatigue Crack Propagation Behavior of TC4 Titanium Alloy for Sports Equipment Prepared by Laser Additive Manufacturing

目的揭示应力比对增材制造TC4钛合金疲劳裂纹扩展行为的影响规律。方法采用紧凑型拉伸试样,在恒载荷幅条件下对激光增材制造TC4钛合金进行了应力比为0.1、0.3和0.5的疲劳裂纹扩展实验,定量评价了不同应力比下合金的疲劳裂纹扩展速率和变化规律。基于Paris公式对裂纹扩展速率进行了拟合,分析了应力比对各参数的影响规律。最后通过扫描电镜对断口表面形貌进行了观察,分析了应力比对断裂模型的影响。结果在相同的∆K条件下,疲劳裂纹扩展速率随着应力比的增大而增大。在Paris公式中,参数C随应力比的增大而减小,参数m随应力比的增大而增大,并且m和lgC呈现线性关系。随应力比的增大,断口表面的河流花样增多、疲劳辉纹变浅、二次裂纹数量增加。结论应力比引起的裂纹尖端闭合效应和平面应力比变化是导致裂纹扩展速率发生改变的主要原因。

The work aims to reveal the effect of stress ratio on the fatigue crack propagation behavior of TC4 titanium alloy prepared by laser additive manufacturing.The fatigue crack propagation experiments of laser additive TC4 titanium alloys with stress ratios of 0.1,0.3 and 0.5 were carried out under constant external load amplitude using compact tensile specimens.The fa-tigue crack propagation rate and change rule of the alloys under different stress ratios were quantitatively evaluated.The crack propagation rate was fitted based on Paris formula,and the influence of stress ratio on each parameter was analyzed.Finally,the surface morphology of the fracture was observed with a scanning electron microscopy,and the influence of stress ratio on the fracture model was analyzed.Under the sameΔK conditions,the fatigue crack propagation rate increased with the increase of stress ratio. In Paris formula, parameter C decreased with the increase of stress ratio, and parameter m increased with the in-crease of stress ratio, and the relationship between m and lg C was linear. With the increase of stress ratio, the flow pattern on the fracture surface increased, the fatigue markings became shallow and the number of secondary cracks increased. The closing effect of crack tip caused by stress ratio and the change of surface stress ratio are the main reasons for the change of crack growth rate.