Effect of Cr content on decomposition behaviour of amorphous Nd5Fe74Cr3B18
Effect of Cr content on decomposition behaviour of amorphous Nd5Fe74Cr3B18
复制标题
Cr含量对非晶Nd5Fe74Cr3B18分解行为的影响
DOI：
10.1016/s1359-6462(99)00376-0
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发表时间：
2000
影响因子：
6
通讯作者：
H. Kanekiyo
中科院分区：
文献类型：
--
作者：
Kiyonori Suzuki;J. Cadogan;M. Uehara;S. Hirosawa;H. Kanekiyo
结果图1显示了非晶态Nd5Fe77-xCrxB18(x=0，3，5)在953K，0.6K下的X射线衍射谱。在0.042 K/S和1.33K/S两种不同的升温速率(α)下，无铬Nd5Fe77B18的X射线衍射图均显示有Nd2Fe23B3、四方Fe3B、α-Fe和NdFe4B4相的反射，表明升温速度对无铬合金的晶化产物影响不大。我们以前的研究已经证实，该合金中α-Fe和NdFe4B4的形成是由于亚稳态Fe3B和Nd2Fe23B3相的分解，因此，在α=0.042~1.33K/S时，非晶态Nd5Fe77B18晶化为Fe3B和Nd2Fe23B3的混合物，在α=0.042 K/S加热的Nd5Fe74Cr3B18样品的衍射图中有明显的相同成分的反射，看不到磁硬的Nd2Fe14B的反射。当升温速率从0.042 K/S增加到1.33K时，同一合金的衍射图发生了明显的变化；在α=1.33K/S下加热的Nd5Fe74Cr3B18样品的衍射图中出现了Nd2Fe14B的反射，而NdFe23B3或NdFe4B4的反射完全消失。这一结果表明，随着加热速度的提高，该合金中前驱体非晶相的晶化过程发生了剧烈的变化，快速加热有利于Nd2Fe14B的形成。另一方面，无论加热速度如何，Nd5Fe72B18Cr5的X射线衍射图中都证实了Fe3B和Nd2Fe14B的混合物的形成。结果表明，对于x=5的合金，晶化后的相组成再次与升温速率无关。
ResultsIn Figure 1, we show the XRD patterns of amorphous Nd 5 Fe 77-x Cr x B 18 (x= 0, 3 and 5) after annealing at 953 K for 0.6 ks. The amorphous samples were heated at two different rates (α) of 0.042 K/s and 1.33 K/s. Both XRD patterns of Cr-free Nd 5 Fe 77 B 18 show reflections from Nd 2 Fe 23 B 3, tetragonal-Fe 3 B, α-Fe and NdFe 4 B 4 phases, indicating that the influence of heating rate on the crystallization products is insignificant for the Cr-free alloy. It has been confirmed in our previous study [5] that the formation of α-Fe and NdFe 4 B 4 in this alloy is due to the decomposition of the metastable Fe 3 B and Nd 2 Fe 23 B 3 phases and hence, amorphous Nd 5 Fe 77 B 18 appears to crystallize into a mixture of Fe 3 B and Nd 2 Fe 23 B 3 at α= 0.042–1.33 K/s. The reflections from the same constituent phases are evident in the diffraction pattern obtained from the Nd 5 Fe 74 Cr 3 B 18 sample heated at α= 0.042 K/s and reflections from magnetically hard Nd 2 Fe 14 B cannot be seen in this diffraction pattern. However, the diffraction pattern of the same alloy changes clearly with increasing heating rate from 0.042 to 1.33 K/s; reflections from Nd 2 Fe 14 B appear and those of Nd 2 Fe 23 B 3 or NdFe 4 B 4 disappear completely in the diffraction pattern for the Nd 5 Fe 74 Cr 3 B 18 sample heated at α= 1.33 K/s. This result indicates that the crystallization process of the precursor amorphous phase in this alloy changes dramatically with increasing heating rate and rapid heating favours the formation of magnetically hard Nd 2 Fe 14 B. On the other hand, the formation of a mixture of Fe 3 B and Nd 2 Fe 14 B is confirmed in the XRD patterns of Nd 5 Fe 72 B 18 Cr 5 regardless of heating rate, showing that the phase constituent after crystallization is again independent of heating rate for the x= 5 alloy.