ABSTRACT

Fe-based nanocrystalline alloy powder prepared by ball-milling is a potential candidate as a soft magnetic composite (SMC). Since the magnetic properties of particles having a random geometry arising from brittle fracture deteriorate by the presence of a demagnetising field, plastically deformed flake-shaped powders, exhibiting better magnetic properties on account of the suppression of any demagnetising field, are desirable. Microstructure such as grain size, lattice distortion and the distribution of dislocations, are affected by ball-milling treatment which changes the magnetic properties. In this study, Fe-based nanocrystalline alloy sheets are ball-milled with lubricant oil as a process control agent (PCA) and the microstructure of the particles investigated. The PCA effectively suppresses the brittle fracture of the alloy sheet during the ball-milling treatment and plastically deformed flake-shaped particles are then successfully obtained. Transmission electron microscopy reveals that there were few lattice defects in the α-Fe grain of the alloy, which indicated that almost only grain-boundary-mediated processes such as GB diffusion/sliding/migration and grain rotation dominate the deformation mechanism. However, Williamson–Hall analysis based on synchrotron radiation exhibits a slope indicating micro-strain in the α-Fe grains. It is found that the plastic deformation induced by the ball-milling treatment forms a microstructure having lattice distortion but containing few lattice defects. It is considered that a slight growth of the existing grains, which can be induced by thermal treatment, can achieve a strain- and dislocation-free microstructure, which is desirable for soft magnetic alloys.

摘要

通过球磨制备的铁基纳米晶合金粉末是软磁复合材料（SMC）的潜在候选者。由于具有由脆性断裂引起的随机几何形状的颗粒的磁性能因退磁场的存在而劣化，因此由于抑制任何退磁场而表现出更好的磁性能的塑性变形的片状粉末是合乎需要的。晶粒尺寸、晶格畸变和位错分布等微观结构受到球磨处理的影响，从而改变了磁性。在这项研究中，铁基纳米晶合金片用润滑油作为过程控制剂 (PCA) 进行球磨，并研究了颗粒的微观结构。PCA在球磨处理过程中有效地抑制了合金板的脆性断裂，从而成功地获得了塑性变形的片状颗粒。透射电子显微镜显示合金的α-Fe晶粒中几乎没有晶格缺陷，这表明几乎只有晶界介导的过程如GB扩散/滑动/迁移和晶粒旋转主导变形机制。然而，基于同步辐射的 Williamson-Hall 分析显示出表明 α-Fe 晶粒微应变的斜率。发现球磨处理引起的塑性变形形成了具有晶格畸变但含有少量晶格缺陷的微观结构。认为可以通过热处理引起现有晶粒的轻微生长，