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摘要本论文运用激光冲击技术，在304奥氏体不锈钢表层引入应变，通过后续热处理来控制表层组织结构。利用扫描电子显微镜(SEM)、光学显微镜研究了激光冲击和激光冲击-退火后奥氏体不锈钢表层组织结构的变化，利用显微硬度计对激光冲击-退火后材料表面硬度进行测试，并总结了不同激光冲击能量下材料剖面硬度梯度分布规律，运用电化学和化学腐蚀实验对处理前后材料的耐腐蚀性能进行测试，并对腐蚀机理进行了分析。实验最后得到以下结论：
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(1)激光冲击在奥氏体不锈钢表面引入应变，表层晶粒内部发生剧烈的塑性变形，在冲击影响层内发生马氏体相变，不锈钢表面显微硬度增加。同时，激光冲击使奥氏体不锈钢的抗晶间腐蚀性能降低。
(2)激光冲击和后续的热处理使得材料的抗晶间腐蚀能力得到明显的改善。激光冲击能量为6J的试样在相同工艺处理下的抗晶间腐蚀性能最好。
(3) 随着退火时间增加，存储的畸变能释放越充分，促进位错迁移，影响伴有孪晶的再结晶晶粒形成，奥氏体不锈钢晶间腐蚀抗力越大，材料越稳定。退火时间为20h时，奥氏体不锈钢抗晶间腐蚀效果最佳。9041
关键词：304奥氏体不锈钢，激光冲击，晶界工程，退火，晶间腐蚀
毕业设计说明书（论文）外文摘要
Title Grain boundary engineering of 304 austenitic Stainless
steel by laser shock assisted
Abstract
The microstructure of the surface layer of 304 austenite stainless steel would be modified through laser shocking processing, which could introduce prestrain in the surface layer of 304 austenite stainless steel, followed by annealing treatment at a higher temperature. EBSD (Electron Back Scatter Diffraction), SEM (Scanning Electron Microscopy) and OM (Optical Microscopy) were used to investigate microstructure evolution of the surface layer after laser shocking processing and laser shocking combined with annealing treatment, micro hardness tester was used to measure the hardness of the surface layer after laser shocking processing and laser shocking combined with annealing treatment, and the hardness gradient distribution law, electrochemical potentiokinetic reactivation (EPR) test and a H2SO4+Fe2(SO4)3 test were carried out to investigate effect of the processing on intergranular corrosion resistance, and the corrosion resistant mechanisms were analyzed as well. The following conclusions were obtained.
(1)Strain could be introduced into the surface layer of 304 austenite stainless steel by laser shocking processing, which resulted in serious plastic deformation of the surface layer of the specimens, martensite phase transformation, and increase of hardness. However, laser shocking processing made the intergranular corrosion resistance of 304 austenite stainless steel decrease.
(2) Laser shocking processing followed by annealing treatment The intergranualr corrosion resistance of the specimens was improved remarkably compared with the based materials by laser shocking processing followed by annealing treatment. The intergranular corrosion resistant performance of the material, whose impact energy was 6J, is the best.
(3) The intergranular corrosion resistance of austenitic stainless steel increased which resulted in dislocation migration and recrystallization grain of twins. The experimental results indicated that the resistant to intergranular corrosion of austenitic stainless steels is the best when the annealing time was 20h.
Key Words:304 austenite stainless steel, laser shocking, grain boundary engineering, annealing treatment, intergranular corrosion.
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