Title: Strong Magnetic Field Effects on the Behavior of Non-Magnetic Particles during Liquid Metal Processing (Effect van sterke magnetische velden op het gedrag van niet magnetische deeltjes in vloeibare metalen)
Other Titles: Strong Magnetic Field Effects on the Behavior of Non-Magnetic Particles in Liquid Metals
Authors: Sun, Zhi
Issue Date: 5-Dec-2011
Abstract: In order to obtain a significant response from a weak magnetic material, a sufficiently strong magnetic field is required which can be introduced by a superconducting magnet. The present thesis is devoted to a quantified research of the strong magnetic field effect on the behavior of weak magnetic particles in a liquid metal. The main research includes three parts: 1) strong magnetic field effects on the behavior of a single particle, 2) strong magnetic field effects on the interaction between particles and 3) strong magnetic field effects on primary crystals during solidification. Liquid aluminum and a Pb-Sn alloy are used to investigate the magnetic field induced segregation/migration of oxide particles. Analytical calculations are at the same time performed to evaluate the magnetic field effects and the behavior of individual weak magnetic particles in liquid metals is summarized. Concerning the magnetic field induced interaction between particles, an additional force due to the liquid metal flow around the particles is, for the first time, defined as ‘magneto-hydrodynamic interaction force’ and analytically estimated under a simplified condition of creeping flow. Although it is difficult to detect the magnetic interaction forces between two micrometer-sized particles directly, experimental results from magnetic field treated samples are used to evaluate the significance of the magnetic interaction forces. A computational fluid dynamics simulation is subsequently carried out to explore the magnetic interaction for higher Reynolds numbers. Under creeping flow limit, the repulsive magneto-hydrodynamic interaction force exhibits a smaller magnitude for smaller particle sizes than the attractive magnetic dipole-dipole interaction force due to magnetization. The repulsive force increases dramatically with particle size and a counterbalancing behavior is observed. A critical particle size exists for which the resultant magnetic interaction force transits from attractive to repulsive. However, when the Reynolds number is high enough, the magneto-hydrodynamic interaction force can also become attractive and may dominate the magnetic interaction. Taking this phenomenon into account, technologies for metallic based materials preparation or particle containing liquid metal processing may be defined. For primary crystals in an undercooled liquid metal, the magnetic field effects are very distinctive. The solidification of Al-Cu alloys in a strong magnetic field is characterized in detail by a series of techniques including SEM, XRD, EBSD, DTA and mechanical property measurement. This research provides evidence that weak magnetic particles in a liquid metal can be manipulated by a strong static magnetic field.
ISBN: 978-94-6018-449-9
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Chemical and Extractive Metallurgy Section (-)
Physical Metallurgy and Materials Engineering Section (-)

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