Memory of texture during HDDR processing of NdFeB
Memory of texture during HDDR processing of NdFeB
复制标题
DOI：
10.1109/tmag.2003.815749
复制
发表时间：
2003-09-01
影响因子：
2.1
通讯作者：
Honkura, Y
中科院分区：
文献类型：
--
作者：
Gutfleisch, O;Khlopkov, K;Honkura, Y
氢化还原脱附复合（HDDR）工艺可获得能量密度超过（BH）（max）= 340 kJ/m（3）的高各向异性和矫顽性NdFeB型粉末。织构诱导是一种非常罕见的现象，其解释具有重大的科学和技术意义。在这里，对Nd12.5FebalB6.3和Nd12.5FebalGa0.3Nb0.3B6.3合金进行了加工，并系统地改变了歧化和复合过程中的氢分压和停留时间。这些工艺参数对显微组织和磁性能的影响进行了描述。中间处理阶段，其特征在于通过Rietveld分析，场发射枪扫描电子显微镜，透射电子显微镜使用EDX和衍射模式。母相，结晶和重组相之间的关系进行了描述，并建议硼化铁相可以作为各向异性介导相在整个过程的不同阶段。在放热结晶过程中，各相的形核和生长受氢分压的控制，从而强烈影响最终的织构程度。这种d-HDDR（动态）工艺产生高度稳定的存储器载体，因此，允许在不添加Co的情况下最大化纹理。据建议，Nb是有用的硼化物相的稳定，而Ga是有益的初始复合过程中。
The hydrogenation disproportionation desorption recombination (HDDR) process can yield highly anisotropic and coercive NdFeB-type powders with energy densities in excess of (BH)(max) = 340 kJ/m(3). The elucidation of-the very unusual phenomenon of texture inducement is of great scientific and technological interest. Here, Nd12.5FebalB6.3 and Nd12.5FebalGa0.3Nb0.3B6.3 alloys have been processed and hydrogen partial pressures and dwell times during disproportionation and recombination have been varied systematically. The effect of these processing parameters on the microstructural and magnetic properties is described. Intermediate processing stages were characterized by Rietveld analysis, field emission gun scanning electron microscopy, transmission electron microscopy using EDX and diffraction modes. Crystallographic relationships between parent, disproportionated and recombined phases are described and it is suggested that the iron boride phase could act as the anisotropy-mediating phase throughout the different stages of the process. The nucleation and growth of the various phases are controlled by the hydrogen partial pressure during the exothermic disproportionation, thereby strongly effecting the final degree of texture. This d-HDDR (dynamic-) process yields a highly stable memory carrier, thus, allowing to maximize texture without Co addition. It is proposed that Nb is useful for the stabilization of the boride phase, whereas Ga is beneficial during initial recombination.