Microstructure And Property Of Ni-Ni₃Si Eutectic In Situ Composites By Directional Solidification

With the rapid development of aerospace technology domestically, and abroad therequirements of new high temperature structure material are extremely severe.Therefore, research and development the new material is very urgent. Ni-Ni₃Si eutecticin situ composite is a potential candidate for high temperature, because it has manycharaters, e.g. high strength, low density and excellent high temperature oxidationresistance, corrosion resistance, etc. However research shows that the brittleness, lowfracture toughness, low and high temperature creep resistance at high temperaturerestrictthe engineering application of the Ni₃Si material. Therefore, new method toprepare the material is of importance both in theory and in engineering application.In this paper, Ni-Ni₃Si eutectic in situ composite is prepared by bridgmandirectional solidification technique and electron beam floating zone melting （EBFZM）technique at the different solidification rates.Microstructures of Ni-Ni₃Si eutectic in situcomposites at different solidification rates are analyzed by metallographic analysis,scanning electron microscopy（SEM）, energy spectrum analysis, microhardness test andXRD phase composition test. The results showed that Ni-Ni₃Si eutectic in situcomposite has the regular lamellar eutectic structure and excellent mechanicalproperties,and Ni-Ni₃Si eutectic is, composed of three phase, Ni matrix phase, Ni₃Sisecond phase and Ni₃1Si12metastable phase, The lamellar spacing is decreased with theincrease of the solidification rate. micro-hardness and plastic show some corresponding laws.As compared with the traditional way of composite materials, eutectic compositesprepared by directional solidification method has many advantages, for example,thepreparation process is simple,the second phase intermetallic compound combined with the matrix closely, lamellar is uniform distributed, etc. This method is a promising onethat can combine material’s preparation technique with and the properties improvementtogether.