Preparation Of Y₂O₃Dispersed Ni-based Alloy By Liquid Phase In-situ Oxidation Reaction And Formation Mechanism Of Y₂O₃

Oxide dispersion strengthened (ODS) Ni-based alloy are strengthened by highmelting point oxide powders (Al2O3, Y2O3, etc).Compared with cast superalloys,ODSalloys avoid the redissolution of the precipitated strengthened phase over hightemperature.So the maximum operating temperature of ODS alloys wouldn’t belimited to the melting point of the precipitated strengthened phase.ODS alloys have awide application prospects in the areas which would face the high temperature andextreme working environment.The common two methods to further improve the high-temperature strength ofalloy are promoting the volume fraction of oxide and refining the oxide particles.However, the conventional mechanical alloying approach is hard to improve the ODSNi-based alloy in these two ways. The excessive addition of oxid powders would leadto the irregularly distributed of particles. On the other hand, during the mechanicalalloying process,ultrafine Y2O3particles tend to react with Al, which is thecomponent element of γ’ phase, and result in coarse products.So it’s necessary to findout new way to prepare ODS Ni-based alloys.This work use liquid phase in-situ oxidation reaction technique to prepare theY2O3nano-particles dispersed distributed Ni-based alloy. In-situ reaction wereperformed over the liquidus temperature of Ni-Y alloy. Choosing the properoxidizing atmosphere can fulfill the preferential oxidation of Y atoms and uniformdistributed Y2O3nano-particles are achieved. To research the influence of reactingtemperature, reacting time and Y content of Ni-Y alloy to the formation and growthof Y2O3particles and reveal the mechanism of in-situ reaction at the liquidustemperature, sample phase and microstructure are characterized.Firstly, Ni(Cu)-Y alloy samples with different Y content prepared by theinduction melting technology. Cu is added as the solid solutions element to adjustsome of the crystal plane spacing of Ni matrix, so it coherent better with the Y2O3particles. Phase and structure information of different samples are obtained fromXRD, optical microscope,SEM and EDS analysis.The result show Y forms Ni17Y2intermetallic compound in the the alloy.Cu is solid dissolve in both Ni lattice and Ni17Y2in quantity.The samples is of typical alloy metallurgical structure.Apply the in-situ oxidation reaction way to the Ni(Cu)-Y alloy of different Ycontent to get the Y2O3dispersed distributed Ni-based alloy, and study the influenceof Y content, oxidation temperature and oxidation time to the phase and structure ofmaterial. The results show that in samples prepared from in-situ oxidation reaction,Y2O3have specific orientation relationship with matrix,(653)Y2O3//(220)Ni.Y2O3particles size increase with the increasing of the Y content in rawmaterial, andspacing between neighboring particles would not be influenced. Y2O3particles sizealso increase with the increasing of reacting temperature, nevertheless it has noobvious relationship with the oxidation time.With the raise of the oxidationtemperature, Y2O3particles size increase and lose the orientation relationship withmatrix.The mechanism of the growth of Y2O3particle is that Y gather and be oxide toform the Y2O3core. Then Ni(Cu) would begin to nucleation on the Y2O3core andgrow with Y2O3till Ni(Cu) totally cover the Y2O3and the growth process finish.