Preparation of superfine Fe-base alloy by liquidus casting
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The superfine Fe–B–Si–Mo and Fe–B–Zr–Nb alloys were prepared by liquidus casting in which the levitation melting combining with the rapid solidification was used. The melt was poured into a copper mold at various temperatures, and a superfine granular microstructure was obtained at liquidus temperature. The behavior of Cu and Ag addition to Fe–B–Si–Mo and Fe–B–Zr–Nb alloys was studied. Both adding Cu and Ag to Fe–B–Si–Mo and Fe–B–Zr–Nb alloys had influence on refining the alloys. The refinement effect of adding Cu is stronger than that of adding Ag in Fe–B–Zr–Nb alloy. I. INTRODUCTION
Since superfine materials possess promising mechanical, magnetic, optical, and electrical properties, which are inherently different from common polycrystalline materials, studies of superfine materials are very popular. Yoshizawa et al.1 first developed the Fe–Si–B–Nb–Cu nanocrystalline which exhibited excellent permeability with a high saturation magnetization.2– 4 However, most superfine materials including nanocrystalline or microcrystalline materials had been prepared by melt spinning, annealing amorphous alloys, ultrasonic atomization, and spray deposition, etc. Although bulk superfine materials have been prepared by some methods such as mechanical alloying and inert gas condensation, etc.,5,6 the processes are complicated and the output is very low, so developing a new preparation technique for bulk superfine materials has grand significance. In this paper a liquidus casting combining levitation melting with high-frequency induction and rapid solidification process has been first used to cast the Fe-base alloy into a copper mold directly and prepare the bulk superfine granular Fe-based alloy, which cannot be obtained by a common rapid solidification process generally. In addition, other elements such as Cu and Au added to Fe-base alloy have influence on refining the grain size.7–12 In this paper, the effects of Cu and Ag on particle size in Fe76.5−xB9Si13.5Mo1(Cu,Ag)x and Fe70−xB20Zr8Nb2(Cu,Ag)x alloys have been studied. II. EXPERIMENT
The Fe–B–Si–Mo and Fe–B–Zr–Nb master alloys were prepared by arc melting 99.99% Fe, 99.99% Si, 99.99% Mo, 99.99% Zr, 99.99% Nb, and lowcarbon Fe–B alloy in an arc furnace with argon atmosphere. The Fe 76.5−x B 9 Si 13.5 Mo 1 (Cu,Ag) x and Fe70−xB20Zr8Nb2(Cu,Ag)x alloys were melted in the fused silica tubes by high-frequency induction and were purified by levitation melting with a specific thermal J. Mater. Res., Vol. 16, No. 12, Dec 2001
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history. The temperature was controlled by an infrared thermal detector. The melt was poured into the copper mold from liquidus temperature 1175 or 1185 °C. The pouring temperature and the levitation force were controlled by adjusting the sample size and the power voltage. Samples that were of about 7-mm diameter and 20-mm high were produced. The samples were cut along the cross section, polished, and etched by a solution of 4% HNO3 and C2H5OH. The specimens were characterized by FEG-XL10 SEM and D/Max-RA x
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