Structural Study of Fe-Based Glassy Alloys with a Large Supercooled Liquid Region
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Structural Study of Fe-Based Glassy Alloys with a Large Supercooled Liquid Region M. Imafuku1, S. Sato1, T. Nakamura2, H. Koshiba3, E. Matsubara4 and A. Inoue4 1 Inoue Superliquid Glass Project, ERATO, Sendai 982-0807, JAPAN 2 Institute for Advanced Materials Processing, Tohoku University, Sendai 980-8577, JAPAN 3 Alps Electric Co, Nagaoka 940-8572, JAPAN 4 Institute for Materials Research, Tohoku University, Sendai 980-8577, JAPAN
ABSTRACT
The thermal stability and local atomic structures of glassy Fe70M10B20 (M = Hf, Zr, Nb, W and Cr) alloys were analyzed by DSC, ordinary X-ray diffraction and AXS measurements. The random network of the trigonal prism-like structure of (Fe,M)3B with edge-sharing, was identified in all the Fe70M10B20 (M = Hf, Zr, Nb, W and Cr) alloys in spite of the wide variety of thermal stability upon heating. Several unique primary precipitated crystalline phases, such as Fe23B6 type and Fe-M phases, were observed in the alloys exhibiting a high thermal stability. These crystallization reactions require relatively long range rearrangements of the constituents and hence the thermal stability of the glassy phase increases, leading to the appearance of a large supercooled liquid region upon heating. These phenomena may be originated from the difference in the chemical affinity and the atomic size mismatch between M and Fe or B.
INTRODUCTION Fe-based glassy alloys with a large supercooled liquid region have been found in a number of multicomponent systems such as Fe-(Al, Ga)-(P, C, B, Si)[1,2], Fe-(Nb, Mo)-(Al, Ga)-(P, B, Si)[3], Fe-(Co, Ni)-Zr-B[4,5], Fe-(Co, Ni)-(Zr, Nb)-(Mo, W)-B[6], Fe-Co-(Nd, Sm, Tb, Dy)-B[7,8]. Much efforts have been paid to obtain the bulk form of these alloys for practical applications. As a result, soft magnetic bulk glassy alloys with diameters up to 5 mm have been successfully obtained by utilizing the high thermal stability of the supercooled liquid in Fe-(Co,Ni)-M-B (M= transition metal of Group IVA, VA and VIA in the periodic table) system[9]. The physical properties of these multicomponet alloys have been also investigated in a wide composition range[10]. Especially, the drastic change in the thermal stability was found by selecting the transition metal, M. According to the Inoue’s design guidelines for bulk metallic glasses[11,12], a kind of unique local atomic structure should play an important role in the suppression of nucleation and crystal growth in these alloys with a particular combination of elements. Therefore, it is important to clarify the local atomic structures in glassy and phase transformation states for these alloys and to discuss the origin of their high glass-forming ability.
L1.6.1
In this study, the local atomic structures of the Fe-M-B (M = Hf, Zr, Nb, W and Cr) glassy alloys were investigated by the ordinary X-ray diffraction and the anomalous X-ray scattering (AXS) methods. We examined the ternary Fe-M-B system for simplicity instead of five component Fe-(Co,Ni)-M-B system because Co and Ni elements were added to improve their ma
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