Solidified microstructure evolution of Mn-Sb near-eutectic alloy under high magnetic field conditions
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Feng Liu State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shanxi 710072, China
Chao Zhang and Jicheng He Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 100036, China (Received 5 October 2008; accepted 1 April 2009)
Mn-90.8 wt%Sb alloys were solidified without and with high magnetic fields to investigate the effects of high magnetic fields on the structure evolution of the alloys. It was found that there were only MnSb/Sb eutectics without any primary phase in the alloy at 0 T, whereas a small amount of primary MnSb dendrites appeared in the MnSb/Sb eutectic matrix when the magnetic flux density was 4.4 T. In magnetic fields of 6.6, 8.8, and 11.5 T, both of two primary phases, i.e., MnSb and Sb, occurred in the matrix. In addition, the volume fraction of these two primary phases increased with increasing magnetic flux density. In magnetic fields of 8.8 and 11.5 T, primary MnSb dendrites aligned parallel to the magnetic field direction and gathered at the edge of the specimens. In contrast, primary Sb dendrites gathered in the center region of the specimens. I. INTRODUCTION
Recently, with the development of superconducting magnet technologies, high magnetic fields >1 T have been available already. Researchers have indicated that the solidification process under high magnetic field conditions is significantly different from conventional one. Except for the well-known fact that the high magnetic field can remarkably suppress the convection in a melt,1 researchers have also found a great number of novel phenomena. Mikelson and Karklin2 carried out solidification experiments of Al2Cu and Cd2Zn alloys with a low cooling rate in 0.5- to 1.5-T magnetic fields and obtained oriented solidified structures. Rango et al.3 performed a solidification experiment of partly melting paramagnetic materials in a 5-T magnetic field and fabricated bulk textured materials, indicating that paramagnetic materials can be oriented by the high magnetic field at high temperature. Morikawa et al.4 observed that nonmagnetic alloys could be aligned during solidification process under high magnetic field conditions. Asai et al.5 reported that, after solidification under high magnetic field conditions, the easy magnetization axis of crystals in the Bi-Sn alloy rotated to the position parallel to the magnetic field direction. Yasuda et al.6 and Li
II. EXPERIMENTAL
An ingot was formed by combining 99.99% pure Mn blocks and 99.99% pure Sb chips followed by induction-melting and quenching under vacuum. The alloy
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0271 J. Mater. Res., Vol. 24, No. 7, Jul 2009
http://journals.cambridge.org
et al.7 extended the alloy system to the Bi-Mn alloy and also observed similar phenomena that the crystals could be oriented by the high magnetic field during the solidification process. Except for the above-mentioned crystal orientation of crystals in
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