机械合金化制备铁基纳米材料的研究

【作者】 程军胜；

【导师】 耿刚强；

【作者基本信息】 长安大学 ， 材料学， 2002， 硕士

【摘要】 本文研究了铁基纳米材料的机械合金化（MA）制备，采用行星式球磨机制得了Fe-Cr-C三元纳米合金粉末。并利用X射线衍射（XRD）、透射电镜（TEM）和穆斯堡尔谱（Mossbauer）等测试方法，对材料在MA过程中的固态相变、成分影响、晶粒以及磁性变化进行了研究。通过试验发现，机械合金化可以加速固态扩散，随着球磨的进行，粉末晶粒尺寸急剧下降，30分钟后达到65.27纳米，20小时后达到4.14纳米；微观应变先增大，10小时达到最大值0.422，随后减小。对穆谱研究发现，粉末晶粒减小导致穆谱峰形宽化，内磁场分布（HFD）减小。根据相变特点将Fe-Cr-C三元合金的机械合金化过程分为三个阶段：物理粉碎阶段、扩散固溶阶段和碳化物析出阶段。机械合金化过程中，碳元素可以促进以Fe₃C为主的碳化物的析出，铬元素使粉末更趋向于非晶态转变，并使材料出现超顺磁现象。此外，还对球磨后的粉末成型工艺进行了探索，提出了改进意见。更多还原

【Abstract】 The ferrous-base nanocrystalline material synthesized by mechanical alloying (MA) was studied. The ternary Fe-Cr-C nanometer alloy powders were obtained in the planetary mill. Through X-ray diffraction (XRD), transmission electron microscopy (TEM) and Mossbauer spectroscopy, evaluated the transformations in solids, the affect of the element and the changing of the grain and the magnetism. The results show that the MA can accelerate the diffusion in solids. During the MA process, the size of grain in the sample sharply decreases to 65.27nm after 30 minute milling and to 4.14nm after 20 hour milling, while the microstrain of the grain increases firstly, reaching the maximum 0.422 after 10 hour milling and then decreases. From the Mossbauer spectra, it can be found that the reduction of grain size can make the spectra line more widen and the decrease of hyperfine field distribution (HFD). According to the characters of transformations in solids, the MA process can be divided into three stages: physical fragmentizing stage, diffusion and solid solution stage, and carbide forming stage. Carbon can promote the forming of carbide of Fe3C mostly during the MA, while it seems that chromium makes amorphism easier. In addition, this paper also made a research on the milled powder forming technology, and presented some improvement methods.更多还原