采用高能短脉宽激光冲击加载技术(LSP),利用扫描电子显微镜(SEM),X射线衍射(XRD)和透射电子显微镜(TEM)等手段,研究了在激光诱导的超高应变率和高于材料动态屈服强度冲击加载条件下,2Cr17Mn15Ni2N奥氏体不锈钢表面亚结构的转变特征和机制。结果表明,冲击区表面结晶度降低,形成大小为0.1～0.5 μm的等轴亚晶区以及规则排列的龟裂区;表面硬度显著增加,形变层深0.25 mm;此外,在冲击区表层观察到形变滞后退火孪晶、显微带、位错胞、条形亚晶、滑移型层错等亚结构,未发现形变孪晶和ε(α)马氏体相。分析认为,激光诱导的超高应变率是产生奥氏体不锈钢表面特殊亚结构的主要原因。

In current study, the laser shock processing (LSP) technique of high energy and short pulse duration is adopted. The substructural transformation characteristics and mechanisms of 2Cr17Mn15Ni2N austenitic stainless steel, subjected to ultra-high strain-rate and impact stress in excess of dynamic yield strength of the target, are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) technology. It is found that the crystallinity in the treated zone is declined, and the size of subgrains ranging from 0.1 to 0.5 μm and the regular arrangement of chapped substructures are formed in the treated region. The hardness in the impacted zone increases apparently and the deformation depth reaches 0.25 mm. Meanwhile, the deformation-lagged annealing twins, microbands, dislocation blocks, streak-like subgrains, slip-type stacking faults, and so on, have been observed in the subsurface of the treated regions. No deformation twin and ε(α) martensite phase are identified. It shows that the ultra-high strain rate induced by LSP plays the crucial role accounting for the unique substructures of the impacted austenitic stainless steel.