Research On Ti-B?B₄C?-Ni-Al Systems Of NiAl Matrix Composite Synthesize By Arc Melting

Ti-B(B4C)-Ni-Al systems of NiAl matrix composites which were fabricated through electric arc melting method was studied in this paper.Differential Scanning Calorimetry(DSC)?X-Ray Diffraction(XRD)?Energy Disperse Spectroscopy(EDS)?Scanning Electron Microscope(SEM)and Transmission Electron Microscope(TEM)have been used to test the reaction mechanism and mechanical properties of the composites.According to the apparent activation energy:It was found that when the reaction system was heated to 917K,Ni Al reacted with Ti to form the transient phase AlNi2Ti,which continued to react with B in 1323K to form ultrafine TiB2 particles as reinforcement agents.The apparent activation energy for these two reactions were calculated and found to be 497.99KJ/mol and 2354.78KJ/mol,respectively.TiC and TiB2 particle(5 vol.%and 10 vol.%)reinforced NiAl matrix composites were fabricated in-situ from Ti-B4C-Ni-Al system through electric arc melting method.It was found that when the reaction system was heated to 905K,Ni Al reacted with Ti to form the transient phase AlNi2Ti,which continued to react with B4C in 1272K to form ultrafine TiC and TiB2 particles as reinforcement agents.The apparent activation energy for these two reactions were calculated and found to be 552.02KJ/mol and 1192.73KJ/mol,respectively.The microstructure and phase component shows that:The sizes of reinforcement TiB2 were mainly 100-500nm,which were distributed on the NiAl matrix evenly.The TiB2 particles had a clear interface.However,the reinforcements TiC and TiB2 particles had aggregated distribution on the NiAl matrix which caused the composites appealing a largr amount of pores.The compressive stretch study shows that:The reinforcement agents had a dispersion strengthening effect on the matrix.The room temperature compressive strength of the composite reinforced by 10vol.%TiB2 particle was measured and found to be 5383 MPa,representing a 35.2%increase over NiAl alloy.The rare earth element cerium was added to refine the grain size which was measured to be 571.1 MPa,representing a 43.5%increase over NiAl alloy.The anti-oxidation study shows that:After high temperature oxidation,the composite material has excellent anti-oxidation performance.Element A1 in TiB2 reinforced NiAl matrix composites and Ti-B4C reinforced NiAl matrix composites is firstly oxidized into stable phase ?-Al2O3.The surface of the composite material added with the reinforcing body becomes uneven after being oxidized,mainly because the formation rate of the oxide film around the reinforcing body is slow,so that a concave part is formed.And the oxide film can creep at high temperature,because the pressure in the mold can be reduced,so that the uneven phenomenon occurs.So that the oxide film can maintain a lower stress level and oxygen can be prevented from reacting with a deeper substrate.