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Modifying agent selection for Al-7Si alloy by Miedema model

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International Journal of Minerals,Metallurgy and Materials 2012年第2期19卷 131-135页

作者： Zhong-wei Chen Cui-ying Ma Pei Chen State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China

To determine the modifying agents for Al-7Si alloys, microstructure observation and mixing enthalpy analysis using Miedema model for Al-7Si alloy with additions of different rare earth elements were performed, and the effects of rare earth elements on the modifica-tion of eutectic silicon morphology were investigated. The results of mixing enthalpy analysis show that these four rare earth elements, La, Sm, Pr, and Ce, which have the large negative mixing enthalpies with Si, can be selected as modifying agents for eutectic silicon morphology. The element with the largest negative mixing enthalpy is Ce. Furthermore, the microstructures indicate that these four elements can effec-tively modify the eutectic （α）Al-Si crystals in Al-7Si alloy, and the most effective one is also Ce. Differential scanning calorimetry （DSC） results show that the eutectic temperature depressions due to the additions of modifying agents are the important reasons for the modification of eutectic （α）Al-Si crystals.

关键词： aluminum alloys silicon alloys modifying agents rare earth elements microstructure enthalpy

WIDE-BAND LASER CLADDING: WEAR AND CORROSION RESISTANCE OF A Ni-BASED ALLOY

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 445-452页

作者： Pan, Q.Y. Huang, W.D. Li, Y.M. Lin, X. Zhou, Y.H. Yang, X.C. Northwestern Polytechnical Univ Xi'an China

A novel wide-band laser cladding system, with high rate of cladding, has been developed in the present work. The system mainly consisted of a 5kW CO2 laser, an automatic powder feeder and a wide-band scanning rotative polygon mirror which can produce a linear or rectangular focused laser beam. Using this system, a Ni-Cr-Si-B alloy powder was cladded on the surface of type 321 austenitic stainless steel in order to improve its wear and corrosion resistance. The pitting corrosion, high temperature oxidation and wear tests were conducted in order to evaluate the properties of the laser cladded layer. The results demonstrated that the cladded layer can significantly improve the adhesive wear and pitting corrosion resistance of the substrate. Moreover, the cladded layer exhibited good oxidation resistance, which is almost the same as that of GMR-235D Ni-based superalloy.

关键词： Boron Chromium alloys Cladding (coating) Laser applications Nickel alloys silicon alloys Wear resistance

NEWLY-DEVELOPED AND CHEAP NANOCRYSTALLINE Fe-Cu-Nb-Mo-Si-B alloys FOR SWITCHING MODE POWER SUPPLY

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Acta Metallurgica Sinica(English Letters) 1997年第6期10卷 489-494页

作者： Zhang, Y.Z. Shanghai Iron and Steel Research Inst Shanghai China

The synthetical soft magnetic properties were reported for newly-developed nanocrystalline Fe73.5Cu1Nb0.9 Mo2.1Si13.5B9 and Fe73.5Cu1Nb0.5 Mo2.5Si13.5B9 alloys. The levels of high-frequency losses of the new alloys are P3/100k=612 and 670 kWm-3, P2/200k=880 and 973kWm-3, P2/500k=4300 and 4600 kWm-3, P0.5/1000k=860 and 920 kWm-3, respectively. They are significantly lower than those of the superior power Mn-Zn ferrite H7c4. The dependence of core loss on frequency and amplitude flux density has been analyzed. The practical applications of the new alloys to switching mode power supplies with the output power of 1 and 2kW were reported.

关键词： Boron Copper alloys Electric power systems Magnetic materials Molybdenum alloys Nanostructured materials Niobium alloys silicon alloys