Solidification Behavior and Cooling Curves for Hypereutectic Fe-21 At. Pct B Alloy
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THE release of latent heat in multicomponent alloys changes the shape of the cooling curve, which can be used to detect the characteristics of transformations and phase reactions during solidification.[1] Accordingly, the cooling curve of solidification was the focus early on, although it is always hard to measure accurately.[2] Rahman et al. used the cooling curve to determine the end point of freezing or glass transition.[3] Farahany et al. used computer-aided analysis to study the effects of bismuth, antimony, and strontium additions on the cooling curves of Al-11.3Si-2Cu-0.4Fe alloy.[1] Gibbs et al. used the cooling curve analysis to determine phase fractions in solid-state precipitation reactions.[4] Djurdjevic et al. studied the effect of Sn on the characteristic solidification temperatures of AlSi6Cu4 alloy.[5] In this work, cooling curves of Fe-21 at. pct B hypereutectic alloy will be shown. Materials with metastable phases have attracted much attention due to their superior properties.[6] The metastable phase solidified from the undercooled melt is always unstable, usually decomposing or transforming to stable phases, so that it cannot be found in the final microstructure.[7,8] However, in the Fe-B alloy, the JUNFENG XU and FENG LIU are with the Department of Metal Material Engineering, Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, Xi’an Technological University, Xi’an 710021, P.R. China, and also with the State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, P.R. China. Contact e-mail: [email protected]. edu.cn ZENGYUN JIAN and BO DANG are with the Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices, Xi’an Technological University. DI ZHANG is with the State Key Laboratory of Solidification Processing, Northwestern Polytechnical University. Manuscript submitted June 30, 2016. Article published online January 13, 2017 METALLURGICAL AND MATERIALS TRANSACTIONS A
metastable phase can remain in the final microstructure when the solidification rate is rapid enough; consequently, this alloy has been the focus of many reports.[9–13] Battezzati et al. studied the thermodynamic data for the stable and metastable phases of this alloy using differential scanning calorimeter (DSC) techniques.[9] Palumbo et al. evaluated the thermodynamic driving forces for crystal nucleation of liquid or amorphous phases, and the competitive nucleation between Fe2B and Fe3B phases was evidenced.[10] Bialiauskaya and Ando developed a method to calculate the nucleation kinetics of monosize droplets of Fe-17 at. pct B alloy with different cooling conditions, and the critical cooling rate for the amorphous solidification was predicted.[11] Yang et al. studied the transformation kinetics of undercooled hypereutectic alloy using the DSC technique,[12] and Yang et al. revealed the metastable eutectic reaction by analyzing the as-solidified structure.[13] The reliable phase diagram information is essential for understanding the transformation in solidifi
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