The Research On Mechanism Of Self-propagating High Temperature Synthesis Of Ti₃AlC₂

Ti₃AlC₂ attracts increasing interest owing to its unique properties.Ti₃AlC₂ combines unusual properties of both metals and ceramics.Like metals,it is a good thermal and electrical conductor,relatively soft and can be easily machined with traditional drill without lubrication or cooling water.Like ceramics,it is elastically stiff:exhibits excellent high temperature mechanical properties.It is resistant to thermal shock and unusually damage tolerant,and exhibits excellent corrosion resistance.These excellent properties mentioned above make it another family of technically important materials.So we conducted the research on the fabrication of single-phase Ti₃AlC₂ material by self-propagating high temperature synthesis and reaction mechanism of Ti₃AlC₂,In order to obtain high pure of Ti₃AlC₂.In the paper,Ti₃AlC₂ were fabricated by self-propagating high temperature synthesis with Ti,Al and C powders.The effect of different technicalparameters(mil -ling parameter test pressu,the ratio of raw materials)on synthesised Ti₃AlC₂ has been studied,In order to find the ideal synthesis conditions.The experiment results show that the main phase of synthesised products is high-purity Ti₃AlC₂ and Ti₃AlC₂ grains are well developed,when used element of powder as raw materials,with raw materials molar ratio of n(Ti):n(Al):n(C)=2:2:1, the mass ratio of steel balls to elemental powder is 15:1,with milling speeding of 120rpm,mixing time for 4-5 hours,under the Ar protection atmosphere in the milling,compacting a sample with the 150MPa pressure.The Ti₃AlC₂ has been successfully prepared by combustion front quenching. Phase transformation and microstructural evolution of the quenched samples were observed by X-ray diffraction(XRD),scanning electron microscope(SEM)coupled with energy-dispersive spectroscopy(EDS)and differential scanning calorimetry (DSC),the mechanism of reaction process and structure forming process were discussed.The results showed the reaction of Ti₃AlC₂ proceeded by a diffusing-dissolving -precipiating-melting-peritecting mechanism.The reaction between Al and Ti partic -les started with the solid-state diffusion reaction at lower temperature,which formed Al₃Ti phase.The melting of Al turn out with the temperature increasing,then the atoms of Ti and C disslove into the Al melt,Al₃Ti will prepicitate from the Ti-Al- C melt;while atoms of Al and C diffusing into the Ti particles,TiC particles will prepicitate from the Ti-Al-C melt as the Ti-C is saturated.when the temperature exceeds the melting point of Al₃Ti,The peritecting reaction betwee TiC and Al₃Ti happened after the melt Al₃Ti melting,which formed Ti₃AlC₂,Ti₃AlC₂ will prepicitate from the Ti-Al-C melt with quick cooling rate.