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利用波长为1.054μm脉宽为20 ns的Nd:glass激光器对表面覆有铝箔的退火态45钢进行了激光冲击处理。用光学显微镜和扫描电镜、X射线应力分析仪及显微硬度计对激光冲击试样的微结构演变、残余应力和硬度分别进行了观察和测试。结果表明,在“完全约束”和几近绝热的条件下,激光诱发的冲击波的超高应变率使45钢表面产生一系列应变效应。激光冲击在试样表面产生的残余压应力可达425 MPa;激光冲击对材料内部各相的显微硬度有显著影响;受激光冲击后,珠光体中的渗碳体依据其位相出现不同程度的破碎现象;先共析铁素体内产生位错和孪晶,形变孪晶呈现薄透镜片状和交互状。
Laser annealing was applied to the annealed 45 steel with aluminum foil coated on the surface with Nd: glass laser with a wavelength of 1.054 μm and a pulse width of 20 ns. The microstructure evolution, residual stress and hardness of the laser impact specimen were observed and tested by optical microscope, scanning electron microscope, X-ray stress analyzer and microhardness tester respectively. The results show that under the conditions of “complete confinement ” and near-adiabatic condition, the ultra-high strain rate of laser-induced shock wave causes a series of strain effects on the surface of 45 steel. The residual compressive stress generated by laser shock on the sample surface can reach 425 MPa. Laser shock has a significant effect on the microhardness of each phase in the material. After laser shock, the cementite in the pearlite appears different degrees according to its phase Broken phenomenon; first proeutectoid ferrite generated dislocations and twins, deformation twins appear thin lens flake and interactive.