Fe含量对快淬SmFe合金结构的影响

Effects of Fe Content on Structure of Rapidly Quenched and Annealed Sm-Fe Alloys

在轮速为40m·s^-1快淬制备不同Fe含量的亚稳态快淬SmFex（x=7．5，8．0，8．5，9．0，9．5，10．0，10．5，11．0，12．0，13．0）合金，经过800℃退火处理60min，采用XRD分析了快淬SmFe。合金退火前后的相组成和晶体结构，并结合Rietveld结构精修方法分析了TbCu7型SmFe9相的晶体结构。结果表明：快淬SmFex合金在化学计量数SmFex（x=7．5—8．0）时，形成Th2Zn17型sm2Fe17和少量的SmFe2；随着Fe含量增加，在x=8．5～13．0时，由平衡相转变成亚稳TbCu7型SmFe9相，a-Fe含量逐渐增多。随着Fe含量增加，SmFe合金的晶格常数a不断减小，而晶格常数c，c／a不断增大。在TbCu，型SmFe9相中Fe原子分别位于2e，3g，6l晶位，Sm原子自由占据1a晶位。2e晶位哑铃状Fe—Fe原子对的的占位趋于无序。退火后SmFex合金在化学计量数x=8．5，9．0时，由亚稳相TbCu7型SmFe9转变为平衡1112znl7型Sm2Fel7相；在化学计量数SmFe，（x=9．5～13．0）时，保持TbCu7型SmFe9不变。退火使2e晶位哑铃状Fe-Fe原子对有序排列，sm原子在la晶位的占位率提高，晶体结构由TbCu，型结构转变成n2zn。7型结构，但Fe含量超过一定值后，无法继续这种转变。退火SmFe，合金晶体结构的晶胞参数变化规律与淬火态相同，退火SmFe合金中a—Fe含量增多。

Metastable SmFe,（x =7.5, 8.0, 8.5, 9.0, 9.5, 10. 0, 10.5, 11.0, 12.0, 13.0） alloys were prepared by rapid quenching and the phases and crystal structure were investigated in the as-quenched state and after annealing at 800 ℃ for 60 min by X-ray diffraction （XRD）. Rietveld analysis was applied to study the crystal structure of SmFe9 phase of TbCu7 type. The results showed that in stoiehiometrie SmFex for x = 7.5 - 8.0, Th2ZnlT-type Sin2 Felt phases and a bit amount of SmFe2 were formed, TbCu7 - type SmFe9 phase rather than Th2Zn17-type structure was obtained by increasing the proportion of Fe （x = 8.5 - 13.0）, and the content of α-Fe increased. Lattice parameters a decreased, hut lattice parameters c and axial ratio c/a increased with the increase of Fe con- tent. Sm was freely located in la position, Fe atoms in 2e site, 3g site, 61 site in TbCuT-type SmFe9 phases and dunbbell pairs of Fe- Fe randomly occupied 2e site. By annealing SmFe, alloys at x = 8.5, 9. 0, Th2Znl7-type Sm2Fel7 phase was obtained from TbCu7-type structure, and at x = 9.5 - 13.0, TbCu7-type SmFe9 phase remained. Fe atoms at 2e site occupied an ordered arrangement, Sm atoms occupying ratio increased＇ after annealing. Th2ZnlT-type structures were transformed from TbCuT-type structure in annealed SmFex al- loys, but this transformation was prohibited when x increased to a certain content. Variation of lattice parameters of annealed Sm-Fe al- loys was the same as the quenched, but ot-Fe increased after annealing.