【作者】 宋宁霞；

【导师】 王东坡；

【作者基本信息】 天津大学 ， 材料加工工程， 2007， 硕士

【摘要】 材料的组织结构直接影响着材料的使用性能,为了满足工作环境对材料的特殊需求,人们提出了多种表面改性技术。与传统的表面改性处理工艺措施相比,超声表面加工处理是一种方便、高效、低成本的方法,它能在金属机械零部件的表面大规模获得纳米结构表层的同时,还获得表面几何形态纳米化,从而提高金属的表面性能。本文采用天津大学焊接教研室研制的TJU-UMSNT-I型超声表面纳米加工处理装置对45钢、40Cr钢和铸铝棒材进行加工处理。利用透射电子显微镜对加工后的样品表面进行微观结构分析,用高精度电感式粗糙度仪对加工后的样品表面粗糙度进行测定,用显微硬度计分析加工后样品的硬度随厚度方向的变化关系,用扫描电子显微镜对摩擦磨损试验后,加工前后样品表面磨损程度进行分析。分析结果如下:(1)经超声表面加工处理后,在45钢、40Cr钢和铸铝的表层形成了等轴纳米晶结构表层,晶粒取向呈随机分布,同时形成了高密度的位错缠结,与原始晶粒尺寸相比,晶粒得到了很大程度的细化。(2)经超声表面加工处理后,45钢和40Cr钢的表面粗糙度显著降低,并形成光洁的表面,表面质量明显提高。(3)经超声表面加工处理后,45钢和40Cr钢的表面硬度与心部相比显著提高,且硬度值随着距表面距离的增大而减小。(4)经超声表面加工处理后,40Cr钢的表面磨擦系数比原始样品的低,且磨损重量有所降低,表面耐磨性得到了提高。更多还原

【Abstract】 The structure of material has direct effect on its usages. People put forward many methods of surface performance improvement to meet the demands of working conditions. Comparing with traditional surface performance improvement technic, ultrasonic surface processing is a convenient, high efficiency and low cost technology. Nanostructured layers were fabricated on the metal machines and parts by ultrasonic processing, as well as geometrical modality nanocrystallization was formed, so the surface performance was advanced.In this paper, the samples of 45 steel, 40Cr steel and aluminum alloy were processed by TJU-UMSNT-Ⅰultrasonic surface nanocrystallization device, which is made in Welding institute in Tianjin University. Observe microstructure on the treated sample by Transmission Electron Microscope, determine the roughness on the treated sample by high precision inductance type roughometer, analyze the relation between the hardness and distance from surface on the treated sample by micro-sclerometer and analyze abrasion degree on the samples treated before and after by Scanning Electron Microscope.Results are as follow:(1) Equiaxed crystal nanostructured surface layers were fabricated on 45 steel, 40Cr steel and aluminum alloy by ultrasonic processing. The grain orientation takes on random distribution, at the same time, high-density dislocation tangle is formed and the grain is highly refined.(2) The surface roughness is significantly reduced of 45 steel and 40Cr steel after ultrasonic processing, smooth surface comes into being and the surface quality is obviously improved.(3) The surface hardness of 45 steel and 40Cr steel highly increased after ultrasonic surface processing, comparing with the center of the samples. Hardness falls as the distance to the surface increases.(4) After ultrasonic processing, friction factor is smaller than original sample of 40Cr, wearing capacity is reduced and surface resistance to abrasion is enhanced.更多还原