Casting Atmosphere Effects on the Precipitates, Magnetism, and Corrosion Resistance of Fe 78 Si 9 B 13 Glassy Alloys
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TRODUCTION
AMONG amorphous alloys, Fe78Si9B13 glass has attracted much attention in recent years, due to its superior performance, i.e., excellent soft magnetic properties, good corrosion resistance, high strength, and so on. Besides, Fe78Si9B13 glass has a good glass-forming ability (GFA) and can be produced at low cost.[1–3] In order to further improve the GFA of Fe-based amorphous alloys, many minor alloying elements, such as Y, Ni, and Cu, need to be added, while other disadvantages appear, such as increased cost and decline of magnetization.[4–6] Generally, to achieve a better GFA, a good vacuum condition and a high purity of elements are necessary, resulting in a high cost and a low economic benefit.[7–11] However, the decrease of casting vacuum results in a better GFA in Fe61Co9Zr8Mo5B17,[12] and even the GFA of some Fe-base alloys can be improved under air atmosphere during the arc-melting process.[13,14] These phenomena were attributed to the suppression of the precipitation of the competitive primary phase due to the effect of a critical level of oxygen.[15,16] Interestingly, hydrostatic chamber pressure has a different influence on the glass formability of Zr65Al7.5Ni10Cu17.5 glass from the Zr65Al7.5Ni10Pd17.5 glass, which is ascribed to the different volume change in L.L. MENG, Master Degree Student, and L. WANG, Professor, are with the School of Mechanical, Electrical and Information Engineering, Shandong University at Weihai, Weihai 264209, P.R. China. X.Y. LI, General Engineer, and J. PANG and L.J. YIN, Engineers, are with Qingdao Yunlu Energy Technology Company Limited, Qingdao 266109, P.R. China. B. AN and W.M. WANG, Professors, are with the Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jingshi Road, Jinan 250061, P.R. China. Contact e-mail: [email protected], [email protected] K.K. SONG, Postdoctoral Student, is with IFW–Dresden, Institut fu¨r Complexe Materialien, Helmholtzstraße 20, 01069 Dresden, Germany. Manuscript submitted March 4, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS A
the primary crystallization;[17] the cooling effect in fabricating Zr65Al7.5Ni10Cu17.5 glass is also dependent on the type of chamber atmosphere.[18] Thus, it is valuable to study the effects of the oxygen element and vacuum degree on the properties of amorphous Fe78Si9B13 alloys. Besides casting atmosphere, the solidification conditions such as super heat, furnace, and melting method can strongly affect the microstructure and properties of the metallic glass. The precipitates in Zr-based glasses and Fe-Cr-Si-B glasses form at high super heat temperature and disappear at lower heat temperature,[19,20] but the precipitation situation in Fe-Si-Nb-Cu-B-Al-Ge glassy ribbons is opposite in the measured temperature range.[21] Meanwhile, the ductility of Mg-Cu-Y-Zn bulk metallic glass fabricated by Bridgman solidification is obviously higher than that by copper mold casting.[22] Among the solidification conditions, the cooling rate is a very importa
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