Fe-metalloids bulk glassy alloys with high Fe content and high glass-forming ability
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The coexistence of high Fe content and high glass-forming ability (GFA) has been earnestly desired from academia to industry. We report a novel Fe76Si9B10P5 bulk metallic glass with an unusual combination of high magnetization of 1.51 T due to high Fe content as well as high GFA leading to a glassy rod with a diameter of 2.5 mm despite not containing any glass-forming metal elements. This alloy composed of familiar and low-priced elements, also exhibiting very excellent magnetic softness, has a great advantage for engineering and industry, and thus should make a contribution to energy saving and conservation of earth’s resources and environment.
I. INTRODUCTION
Recently, Fe-metalloid (B, C, Si, P)-based ferromagnetic bulk metallic glasses (BMGs) containing glassforming metal elements such as Al, Ga, Nb, Mo, and Y have been developed.1–7 These alloys exhibit glass transition and supercooled liquid regions before crystallization and have a relatively high glass-forming ability (GFA) leading to the formation of BMG rods specimen with diameters on the millimeter order prepared by Cumold casting, which has much lower cooling rates than melt-spinning used for the production of the Femetalloid-based amorphous alloy ribbons with a thickness of less than about 50 m. The BMGs have removed the restriction of the melt-spun amorphous ribbons without grass transition. However, the glass-forming metal elements in BMGs result in a remarkable decrease in saturation magnetization (Js) from 1.5–1.6 T of the representative Fe–Si–B amorphous alloys widely utilized by industries to less than about 1.3 T. The magnetic elements such as Co and Ni also have some beneficial effects on the GFA8,9 in most cases. However, the addition of these elements to Fe-based BMGs significantly decreases Js in the same manner as the glass-forming elements. The substitution of Co for Fe at 50% in (Fe0.75Si0.10B0.15)96Nb4 (all compositions are in at.%) significantly increases the critical rod size of 1.5–5 mm in diameter, which is the largest size among the soft magnetic BMGs produced by Cu-mold casting; however, Js rapidly decreases to 1.1 T.8 The low Js of the BMGs is a great disadvantage for soft magnetic materials. In ad-
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0180 J. Mater. Res., Vol. 23, No. 5, May 2008
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dition, these metal elements are rare and expensive, and Al, Nb, Mo, and Y also decrease productivity due to their tendency toward oxidation. Thus, it would be better to avoid the use of these metal elements in favor of those with high Js, less-harmful effect on the environment, and lower material cost. Therefore, the development of Febased BMGs without any metal elements other than Fe and with relatively high Fe content have been desired for the last one decade; however, this need has been left unresolved for many years.
II. EXPERIMENTAL PROCEDURE
Fe–Si–B–P ingots were prepared by induction melting the mixture of pure metals of F
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