Research On Fabrication And Properties Of TiC??-Al₂O₃?/NiAl Composites By Arc Melting

The NiAl intermetallic compounds with high melting point,high thermal conductivity and good oxidation resistance are considered to be one of the most promising high temperature structural materials for wide application.In this paper,in-situ TiC/NiAl and?TiC+?-Al₂O₃?/NiAl composites were fabricated by arc melting in Ti-C-Ni-Al and TiO₂-Ti-C-Ni-Al systems.Differential Scanning Calorimetry?DSC?,X-ray Diffraction?XRD?,Scanning Electron Microscope?SEM?and Energy Dispersive Spectroscopy?EDS?were used to study the mechanism of reaction,micro-structure,room temperature compression performance and high temperature oxidation resistance with different systems.The mechanism of reaction shows that in Ti-C-Ni-Al system,the exothermic reaction of Ni and Al occurs at 907K,which initiates the reaction of Ti and C to form TiC,and TiC/NiAl composites are obtained.The equations of reaction are:Ni+Al?NiAl;Ti+C?TiC.In the TiO₂-Ti-C-Ni-Al system,the exothermic reaction of Ni and Al occurs at 905K,which initiates the reaction of Al and TiO₂ to produce?-Al₂O₃ and[Ti].The reaction of C and Ti forms TiC,resulting in?TiC+?-Al₂O₃?/NiAl composites.The reaction equations are:Ni+Al?NiAl;3TiO₂+4Al+5Ti+8C?2?-Al₂O₃+8TiC.Micro-structure studies show that in TiC/NiAl composite,TiC is cuboidal,with a size of5-10?m,distributed in the NiAl matrix.In the?TiC+?-Al₂O₃?/NiAl composite,TiC are partially segregated around?-Al₂O₃ particles,and TiC particles are 2-5?m,and the?-Al₂O₃particles are 8-20?m.The addition of CeO₂ promotes the uniform distribution of reinforcement.The performance of room temperature compression reveals that NiAl is mainly a cleavage fracture in the compression experiment,and the composite material is a quasi-cleavage fracture with partial plastic fracture characteristics.The compressive strength of NiAl is 618.3MPa in room temperature,and the compressive strength of the composite is significantly improved.The addition of CeO₂ can further improve the compressive strength of the composite.In this experiment,the compressive strength of 10vol.%TiC/NiAl composite with CeO₂ added in an amount of 1wt%reaches 1329.8MPa,which is about 110%higher than that of the matrix material.High temperature oxidation resistance studies show that the oxide film of NiAl changes from ?-Al₂O₃ to?-Al₂O₃ at the temperature of 1273K.Oxide peeling occurs in some areas,and the inside of the material is further oxidized.TiC/NiAl and?TiC+?-Al₂O₃?/NiAl composites with CeO₂ addition amount of 1wt% and volume fraction of 10%.When the oxidation temperature is 1273K,TiC particles are oxidized to TiO₂,which grows continuously and has obvious growth steps.The continuity of the?-Al₂O₃ oxide film on the surface of NiAl is destroyed.The oxide film is closely bound to the matrix and inhibits the formation of voids between the oxide film and the matrix.