氩气氛围下Ti_(6)Al_(4)V纳秒激光抛光机理及显微硬度研究

Study on the Mechanism and Microhardness of Ti_(6)Al_(4)V Nanosecond Laser Polishing in Argon Atmosphere

研究氩气氛围下钛合金Ti_(6)Al_(4)V激光抛光作用机理对提高材料表面质量和使役性能具有重要意义。采用纳秒脉冲光纤激光器以弓字形扫描路径抛光8 mm×8 mm局部钛合金区域。运用偏光显微镜、光学表面轮廓仪观察抛光后材料表面形貌并测量材料表面粗糙度,研究不同平均功率、光斑重叠率、脉冲宽度、扫描次数及不同原始表面粗糙度对钛合金表面粗糙度的影响规律。通过全自动显微硬度仪、扫描电子显微镜、X射线衍射分析仪分析抛光后材料钛合金Ti_(6)Al_(4)V组织性能。试验结果表明:随着激光平均功率、光斑重叠率和扫描次数的增大,钛合金表面粗糙度先减小后增大。随着脉冲宽度的增加,钛合金表面粗糙度呈下降趋势。原始表面粗糙度越大,抛光后表面粗糙度缩减率越大;原始表面粗糙度越小,抛光后表面粗糙度越小。试验获得的最小钛合金表面粗糙度Ra=0.164μm,表面粗糙度缩减率为60%,抛光后材料表面显微硬度相对于基体提高了6%。抛光后钛合金表面组织由白色等轴状转变为细针状马氏体。

Study on the mechanism of laser polishing of titanium alloy Ti_(6) Al_(4) V is of great significance to improve the surface quality and performance. A nanosecond pulsed fiber laser was used to polish an 8 mm×8 mm local area of the titanium alloy with a bow-shaped scanning path. Polarized light microscope and optical surface profilometer were used to observe the two-dimensional and three-dimensional morphology of polished material surface and measure the surface roughness. The effect of different laser power, overlap rate, pulse width, scanning times, and surface roughness on the surface roughness of titanium alloy was studied. The properties of the polished materials were analyzed by automatic microhardness tester, scanning electron microscope and X-ray diffraction analyzer. The results show that with the increase of the average laser power, the spot overlap rate and the scanning times, the surface roughness of the titanium alloy decreases first and then increases. With the increase of pulse width, the surface roughness of titanium alloy shows a downward trend. The greater the original surface roughness is, the greater the reduction rate of the surface roughness polished will be. The smaller the original surface roughness is, the smaller the surface roughness polished will be. The minimum surface roughness of titanium alloy is 0.164 μm, and the roughness reduction rate is 60%. The microhardness of the polished material was increased 6% compared with the matrix. After polishing, the surface structure of the titanium alloy changes from white equiaxed α-Ti_(6) Al_(4) V to fine needle-like martensite α′-Ti_(6) Al_(4) V.