Local structure changes of Ga during nanocrystalline formation from melt-quenched Fe73Ga4Nb3Si11B9 alloys
Local structure changes of Ga during nanocrystalline formation from melt-quenched Fe73Ga4Nb3Si11B9 alloys
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熔融淬火 Fe73Ga4Nb3Si11B9 合金纳米晶形成过程中 Ga 的局部结构变化
DOI：
10.1088/0953-8984/7/35/016
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
T. Tomida
中科院分区：
文献类型：
--
作者：
M. Matsuura;M. Sakurai;Sang;Kenji Suzuki;T. Tomida
为了揭示Ga、Nb在非晶态Fe73Ga4Nb3Si11B9合金纳米晶形成中的作用，对非晶态Fe73Ga4Nb3Si11B9合金在不同温度下退火后的Ga K边和Nb K边进行了XAFS测量。XAFS结果表明：与Fe_(73)Ga_4Nb_3Si_(11)B_9(FINEMET)不同，在α-铁沉淀温度TX1以上退火的样品，Ga没有明显的Ga偏聚，表明Ga原子替代位于体心立方铁位置。曲线拟合分析表明，退火后Ga原子的配位数在TX1处有所下降，但在TX1处又上升到TX1以上，这表明在α-Fe析出开始时，Ga原子倾向于被排除在B和Si比其他原子丰富得多的边界上。Ga的这种瞬时排斥效应可以归因于这些合金的纳米晶的形成。Nb在Fe73Ga4Nb3Si11B9中起着与FINEMET相同的作用，即抑制α-Fe的晶体生长，抑制Fe-B化合物的形成。
XAFS measurements of the Ga K edge and the Nb K edge have been carried out for amorphous Fe73Ga4Nb3Si11B9 alloy after annealing at various temperatures in order to reveal the roles of Ga and Nb in the nanocrystalline formation. XAFS results show that: there is no definite Ga segregation, unlike Cu in Fe73Ga4Nb3Si11B9 (FINEMET) XAFS spectra of Ga for the samples annealed above the alpha -iron precipitation temperature, Tx1, indicate that Ga atoms sit substitutionally at bcc iron sites. Curve fitting analyses of the XAFS of Ga show that coordination number after annealing drops at Tx1 but it rises again above Tx1, which suggests that at the beginning of alpha -iron precipitation, Ga atoms are inclined to be excluded toward the boundary where B and Si are much more abundant than other atoms. Such a transient exclusion effect of Ga can be attributed to the nanocrystalline formation of these alloys. Nb in Fe73Ga4Nb3Si11B9 seems to play the same role as that in FINEMET, i.e. retarding crystal growth of alpha -iron and suppressing Fe-B compound formation.