【作者】 唐锋林；

【导师】 张喜燕；

【作者基本信息】 广西大学 ， 材料学， 2008， 硕士

【摘要】 表面纳米化技术是一种针对材料表面进行处理的加工工艺,它一方面使材料具有了纳米材料优良的表面性能,另一方面使材料仍保留心部粗晶材料较好的抗蠕变性能,因此近年来表面纳米化技术普遍受到材料学界的关注,同时表面纳米化技术也对纳米材料应用于实际生产生活创造了一条新路。本文重点研究高能喷丸对A04112铝合金和AZ91D镁合金表面纳米化后力学性能和电化学性能的改变。高能喷丸处理后,金属最表面层出现纳米结构晶粒,晶粒大小从基体区到表面层呈梯度变化,晶粒逐渐变小,表面硬度和强度也逐渐升高,表面电化学性质发生改变,更容易形成致密氧化膜,从而对基体有更好的保护作用。因此我们利用显微硬度分析、X射线衍射分析、光学显微镜和扫描电子显微镜分析、能谱分析和阳极极化方法分别对铝合金和镁合金喷丸后的性能进行了研究,得到以下结论:关于晶粒细化和力学性能的研究,可以发现A04112铝合金和AZ91D镁合金在喷丸后表面层的晶粒非常细小,无法分辨,但随着晶粒至表面间距离的增加,晶粒逐渐可以分辨,这表示晶粒已逐渐变大。通过对喷丸后最表层的XRD分析,可以计算出A04112铝合金喷丸后表层晶粒大约为109nm,AZ91D镁合金喷丸后晶粒大约为68nm,可见铝合金和镁合金喷丸后表层晶粒都得到了显著的细化。由OM照片和SEM照片还可以粗略估算出镁合金细化层的厚度在200μm左右,铝合金细化层的厚度约120μm,这与显微硬度分析得出塑性变形影响层的厚度基本一致。另外通过研究AZ91D镁合金在不同热环境下晶粒的长大情况和峰位偏移情况,可以分析出其喷丸后纳米结构的热力学稳定性在200℃以内,当温度再升高时,晶粒将出现以动态再结晶为特征的晶粒长大,晶格畸变情况有明显改善,表面纳米化层随之失效。关于电化学性能的研究,可以发现A04112铝合金和AZ91D镁合金在喷丸后自腐蚀电位有所提高,自腐蚀电流也相应降低,这说明喷丸后的铝合金和镁合金比喷丸前的耐蚀性能有较大的提高。通过能谱仪观察铝合金在喷丸后表面形成的氧化膜,可以发现其有较好的耐蚀性,对基体有很强的保护作用,镁合金喷丸后形成的氧化膜虽然抗蚀性能也有所提高,但并没有根本性地改变,在腐蚀环境下对基体仍不能形成有效保护。更多还原

【Abstract】 Surface nano-technology is a kind of surface treatment in material processing technology, which can make the materials’ surface have excellent performance of the nano-materials, and the treated materials can remain the anti-creep property of the coarse grained material. In recent years, surface technology has been the concern of academics, and the surface technology has created a new path for nano-materials used in daily life.In this paper, we focus on the change of mechanical and electrochemical properties taken by high-energy shot peening on the surface of Al and Mg alloy. After the shot peening, we can find that the grains on the most surface are so fine that it can’t be distinguished. However, as the grains far away from the surface, the grains get bigger, and the surface hardness and stress decreased gradually, the electrochemical changes as the the size of grain increased at the same time.We use micro-hardness analysis, X-ray diffraction, optical microscope and scanning electron microscopy analysis, EDX analysis and anode polarization methods to study the performance of shot-peening Al and Mg alloy, and received the following conclusions:About the grain refinement and mechanical properties, we can find that the grains on the surface are so fine that the grains can not be distinguished, but with the distance to surface increased, the grain can be gradually distinguished, which means that the grain get bigger. Form the XRD analysis, it can be calculated that the grain in the most surface of Al alloy is around 109 nm, and it is about 68 nm in Mg alloy’s surface. From OM and SEM photos, we can roughly estimated that Mg alloy’s treated surface is about 200μm, and Al alloy’s treated surface is about 120μm, which is according with the result of micro-hardness experiment.In addition, through the research on Mg alloy’s grain grown up and the peak migration in different thermal environment, we can known that Mg alloy’s nano-structure can stand within the 200℃, when the temperature go to rise, Grain appears to be crystallization of grown up, and lattice distortion situation has improved significantly, nano-surface failed at the same time.About the electrochemical properties, we can found the shot peening Al and Mg alloy’s anode potential have increased, and the corrosion current correspondingly decreased, which indicating that shot peening Al and Mg alloy’s Corrosion resistance have increased. Through the EDX of the shot peening Al alloy’s surface, we find that it have a better corrosion resistance than before, and it has a strong protective effect to the matrix. Although the anti-corrosion properties of shot peening Mg alloy has been upgraded, but there is no fundamental change, and it still can not provide an effective protection to the matrix.更多还原