E690高强钢表面激光冲击微造型的模拟与试验

Numerical Simulation and Experiment Micro-dimple Array on E690 High-strength Steel Surface Induced by Laser Shock Processing

为研究冲击次数对E690高强钢表面激光冲击微造型、表面残余应力和微观组织的影响,采用有限元软件ABAQUS模拟试样表面成型过程,使用7.96 GW/cm^2的脉冲激光冲击E690高强钢试样,采用光学轮廓仪测量试样表面三维形貌,利用X射线应力分析仪测量激光冲击微凹坑表面的残余应力并提取半高宽值,利用TEM观察冲击区域的微观组织形貌。结果表明,使用7.96 GW/cm^2的脉冲激光冲击试样1~4次,深度在10~40μm呈增加趋势,在深度方向对比试样表面三维形貌的模拟结果和测试结果,误差范围合理;激光冲击2次及以上,试样测点各方向残余压应力测试值趋于一致;半高宽值逐渐增大,冲击4次与冲击3次的半高宽值趋于相等;冲击2次后试样的TEM像和电子衍射图表明微凹坑表面形成了纳米晶。

To study how different times of laser shocks affect the micro-dimple, surface residual stress and microstructure of E690 high-strength steel, the finite element software ABAQUS was used to simulate the surface evolution process of the sample. E690 high-strength steel specimens were impacted by pulsed laser with a power density of 7.96 GW/cm^2. Threedimensional surface morphology was measured by an optical profiler. The surface residual stress and FWHM values of lasershocked zone were measured by an X-ray diffraction residual stress tester, and the microstructure and morphology of the impacted area were characterzal by using TEM. Results show that when pulse laser with a power density of 7.96 GW/cm^2 impacts 1-4 times, the resultant depths present an increasing trend between 10 and 40 μm. A comparison of the simulated and measured results of three-dimensional surface topography in depth-wise direction suggests that the error rate falls within a reasonable range. When pulse laser impacts 2 times and more, test values of residual compressive stress of the specimens tend to be consistent in all directions. FWHM values gradually increase and tended to be equal with the impact being performed 4 and 3 times. TEM images and electron diffraction patterns of specimens that has been impacted by pulse laser for 2 times show nanocrystals forming on the surface of the micro-dimple.