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Study on Microstructure and Mechanical Properties of Iron-aluminide Intermetallics Prepared by Microwave-assisted Combustion Synthesis

Author: WeiZuo
Tutor: KongJian
School: Nanjing University of Technology and Engineering
Course: Materials Science
Keywords: microwave-assisted combustion synthesis nanocrystalline iron aluminides intermetallics friction wear
CLC: O611.3
Type: Master's thesis
Year: 2009
Downloads: 63
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Abstract


Iron-aluminide intermetallics were prepared by microwave-assisted combustion synthesis technology,based on raw materials of Al and Fe2O3 powders.A series of iron-aluminide intermetallics（the contents of Al at.%:21%,25%,28%,32%,36%） were prepared by adjusting the proportion of mixture.The effect of Al content on microstructure and properties was investigated.The microstructure and properties of Fe-28Al alloy were also studied after addition of 3 at.%Cr.The adiabatic temperature(Tad) of reaction system was calculated by using thermodynamics theory.From the point of view of thermodynamics,the cause of reaction generation was analyzed,and the variation of Tad with different content of Al,as well as the effect of Tad on microstructure formation was investigated.In addition,the mechanism of microstructure formation was discussed.The results indicate that bulk nanocrystalline Fe-Al intermetallics are successfully prepared by microwave-assisted combustion synthesis.The microstructure of products is nanocrystalline Fe3Al matrix with the grain size of 30nm～50nm dispersed with acicular and granular phase of Fe3Al with several hundred micrometres order of magnitude.In the range of stoichiometric composition of Fe3Al,microstructure with nanocrystalline is obtained when Al content is altered.The acicular phase in non-stoichiometric composition is coarser than that of Fe-25Al alloy with stoichiometric composition.The solidification microstructure is characterized with dendrites when Al at.%reaches 36%.Acicular phases in the microstructure of Fe-28Al disappear after addition of chromium,and a large number of granules appear in Fe-28Al-3Cr.Compared with conventional casting Fe-25Al,the microhardness and wear resistance of iron aluminides prepared by microwave-assisted combustion synthesis increase obviously. The microhardness of Fe-Al alloys with different compositions is about 420HV～650HV,and the casting Fe-25Al is 250HV on average.And the wear rate is one order of magnitude lower than that of casting.The wear resistance increases with the increase of Al content.Compared with Fe-28Al alloy,microhardness of Fe-28Al-3Cr alloy is little affected by chromium addition,while the wear rate is decreased.

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