Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Physics of metals > The liquid structure of the metal and solidification theory

Effect of Electromagnetic Field on the Fe-Si Impurity Phases of Solidified Commercially Pure Aluminum

Author DuYuHua
Tutor CuiJianZhong
School Northeastern University
Course Materials Processing Engineering
Keywords Industrial aluminum Macro- organization Microstructure Magnetic field Electric field Fe-Si impurity phase .
CLC TG111.4
Type Master's thesis
Year 2008
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Pure aluminum has a series of excellent performance, a wide range of applications in various sectors of our national economy. Performance and organizational structure of the material is closely related, so the research and analysis of the pure aluminum solidification structure has an important role and significance. Other hand, in the solidification process of the material applied to the electromagnetic field, interested in the metal solidification process have a significant impact, and also has important implications for the preparation of new materials. Therefore, the basic phenomenon of industrial aluminum in the the solidification structure under the electromagnetic field, and to explore the mechanism of action of the electromagnetic field. Including the DC magnetic field, AC magnetic field, DC gradient magnetic field, AC current, and current and magnetic field together for the impurity phase distribution, shape, size; of intragranular solute content, phase composition, lattice constant, and the relative orientation of the impact. The study of these basic questions, rich material electromagnetic process theory, laid the foundation for future research work. This paper the following conclusions: (1) treatment of the magnetic field, DC magnetic field had no significant effect on the grain size, increase in kanji-like, bone-like tissue sample; alternating magnetic field so that the grain, fan-shaped columnar crystals, impurities heart to the sample Department gathered impurity phase on the entire sample crushing. (2) sample after magnetic treatment, β-AlFeSi phase decreases, α-AlFeSi phase increases AC magnetic field treatment sample the α-AlFeSi with the most abundant. This shows that the processing of the magnetic field can promote the formation of α-AlFeSi phase. In addition, the treatment of the alternating magnetic field, the sample FeAl3 phase increased. Other hand, the magnetic treatment to increase the concentration of Fe, Si atoms in the Al matrix. (3) DC gradient magnetic field because of its gradient is small, and the melt is, in a very short period of time the solidified, so the grain size is not significantly affected. After the processing of the gradient magnetic field, impurities opposing magnetic field strength enhanced direction aggregation of most of the impurities in the sample phase finely, was short rod arranged in the grain boundary. (4) AC electric field processing grain refinement. 8A (current density 39.31mA/mm2) exchanges under current conditions, the cooling rate ° C / min, the effect of microstructure refinement, the central organization of the sample size is only 1/7 of the outfield, the impurity phase content than No external field under the condition of at least 1/3; the small size of the impurity phase, the diameter of about 2μm. Microstructure refinement, the impurity phase ball, help to improve the plasticity of the aluminum industry. The electric field treatment of the increase in aluminum by the concentration of Fe, Si atoms in solid solution in the matrix and Si reduce segregation. XRD analysis showed that, compared with the non-outfield processing of the sample, the current treatment, the sample near the top electrode impurity phase α-AlFeSi phase increases the, Al6Fe phase to reduce phase disappears, FeAl3. (5) a suitable electromagnetic field parameters, it is possible to obtain fine-grained structure. The electromagnetic field treatment, the intragranular Si, Fe content is substantially increased, and the Si reduce segregation. I = 16A, B = 0.34T, the grain boundary become thin, and the impurity phases become the crushing phase transition short rod-phase or massive phase. XRD analysis showed that, compared with the non-outfield processing of the sample, the electromagnetic field treated sample at the top of α-AlFeSi phase to reduce or even disappear, β-AlFeSi phase disappears; specimens the Central, β-AlFeSi phase to reduce.

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