Effects of High Magnetic Fields on the Distribution and Alignment of Primary Phases in an Al-12Si-11.8Mg-6.5Ti Alloy
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RECENTLY, considerable efforts have focused on the research of materials processing by using a high magnetic field with the development of superconducting magnet technology. Now, the application of high magnetic fields is expected as one of promising technologies in materials processing[1–3] because of the enhancement both in Lorentz force and magnetization.[4,5] Especially in the solidification process, the effect of high magnetic fields is more obvious because of the occurrence of phase transformation and various electromagnetic performances, such as relatively higher electric conductivity of a melt. On the one hand, the Lorentz force has long been recognized to influence the thermosolutal buoyant flow significantly in a melt and thus influence the temperature and solute fields.[6,7] On the other hand, in terms of the enhanced magnetic force, by which even nonmagnetic materials could also show obvious response to the high magnetic field,[8,9] several interesting phenomena such as magnetic levitation[10,11] and magnetic separation[12,13] have been realized. Moreover, depending on the magnetic anisotropy of crystals, which can induce the difference of magnetization energy in various crystallographic directions, some oriented or textured structures have be prepared by high magnetic fields.[14–16] Using some selected binary alloys, several studies were carried out to investigate the distribution and TIE LIU and CHUNJIANG WANG, Doctoral Students, QIANG WANG and JICHENG HE, Professors, HUTIAN LI, Postdoctor, and ZHONGYING WANG, Graduate Student, are with the Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110004, P.R. China. Contact e-mail: [email protected] Manuscript submitted June 2, 2010. Article published online December 8, 2010 METALLURGICAL AND MATERIALS TRANSACTIONS A
alignment behaviors of primary phases of these alloys during the solidification process in high magnetic fields. By adjusting the direction and value of the magnetic field gradients, the distribution of the primary phases in the final structures of the alloys was successfully controlled.[17–19] Meanwhile, by combining magnetic crystal orientation, magnetic dipole– dipole interactions, and crystal growth feature, a series of structures with the primary phase highly aligned has been obtained.[20–23] However, those previous studies have been limited mostly to the systems that generally have only one primary phase; no comprehensive study on the effect of high magnetic fields on the distribution and alignment behaviors of primary phases of a complex alloy system that has several primary phases has been available thus far. During the solidification process of such a system, different primary phases will precipitate from the melt at different stages with decreasing temperature; these phases have different properties, and the high magnetic field thus should exert different effects on the migration and morphology of these phases. In the current study, a complex alloy of Al-12Si11.8Mg-6.5Ti (mass percentage) has b
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