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摘要金属材料表面纳米化可以在不改变材料原有的化学成分和外观形貌的基础上制备从表面到基体连续过度的纳米结构层，以提高材料的整体性能和环境服役性能。金属材料表面纳米化是金属材料改性的发展方向，具有良好的应用前景。
- 上一篇：不锈钢Al-Si合金脱氧产物形貌研究
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本课题用弹丸喷丸处理引起材料表面的强烈塑性变形，从而在材料表面制备纳米结构表面层。试验所用试样为316L不锈钢，对试样进行表面纳米化处理后运用金相显微镜、扫描电子显微镜、显微硬度计等试验研究设备对试样的显微结构变化进行研究。结果表面：经弹丸喷丸处理后，316L不锈钢表面晶粒细化至纳米量级；沿着厚度方向晶粒尺寸呈梯度分布，从试样表面到基体晶粒逐渐增大至原始晶粒尺寸；表面纳米结构层显微硬度显著提高，最高可达365HV，相对于基体硬度的175HV提高了近两倍，且随着距表面层深度的增加显微硬度逐渐增加，与材料显微结构的变化相吻合；经表面纳米化处理后试样的抗拉强度为630MPa，较原始试样的320MPa，表面纳米化后试样抗拉强度提高了两倍；平均塑性变形率为25%，表明表面纳米化能显著提高材料表面的强度与硬度，但会降低材料的塑性与韧性。22364
关键词：316L不锈钢；表面纳米化；显微组织；显微硬度
毕业论文设计说明书（论文）外文摘要
Title Mechanical properties of surface nanocrystallization
316L stainless steel
Abstract
Metallic material surface nanocrystallization could produce gradient nanostructure from the surface to the substrate layer , in order to improve the overall performance and environmental service performance of the material ,but would not change the original chemical composition and appearance of the material. Metallic material surface nanocrystallization is a developed topic to modify the metal material,and it has a promising application prospect.
The topic of this project is to induce strong plastic deformation of the surface of metal material through Rotational Assisted Shot Peening to make the preparation of nanostructure surface layer in the surface of metal material.
The experiment choose 316L stainless steel as test sample,after surface nanocrystalliation of the sample, metallographic microscope and scanning electron microscope were use to study the change of microstructure of the sample. Hardness tests and tensile tests were used to test the mechanical properties of the treated 316L stainless steel.
The result shows that : after the shot peening treatment of the surface ,the surface grains of 316L stainless steel were refined to the nanometer level;Grain size is gradient distributed along the thickness direction , and the size of grain gradually increased from the surface nanosturcture to the original coarse; the micro-hardness of the nanometer structure layer significantly increased 365HV , doubled of the hardness of the original material ; and with the increase of the distance from the surface layer , the micro-hardness decrease , and it is conformity with the change of the microstructure of the material ; through RASP treated , the tensile strength of the samples is630MPa, and final elongation is 32% , and it show’s that surface nanocrystallization can significantly improve the strength and hardness of the surface layer ,but would reduce the plasticity and toughness of material.
Keywords: 316L stainless steel; surface nanocrystallization; microstructure; micro-hardness
目录
1 绪论 1
1.1本课题研究背景 1
1.2表面纳米化介绍 1
1.3不锈钢表面纳米化现状与发展问题研究 6
1.4本课题所研究的问题及采用的研究方法 6
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