Synthesis Of High-purity Ti₃AlC₂by Spark Plasma Sintering And Strengthening By Substituting Al With Si

The ternary compound Ti₃AlC₂as a new structural materials, possesses an unusuallycombined properties of both metals and ceramics that has a broad application prospect. Inthis paper, we take Ti/Al/C mixed powders as raw materials. High purity Ti₃AlC₂wassynthesised by spark plasma sintering（SPS）. The reaction mechanism and the influence ofsintering parameters were studied by X-ray diffraction （XRD）, scanning electronmicroscopy （SEM） and transmission electron microscopy （TEM）. The strengthening ofTi₃AlC₂was studies by incorporation Si to form Ti₃Al_1-xSi_xC₂solid solutions.The ratio of raw materials was primary factor to influence the purity of Ti₃AlC₂fabricated by SPS from Ti/Al/C system. High purity and high density sample was obtainedby sintering3Ti/1.1Al/1.9C mixed powders at1350℃under a pressure of30MPa for10min. The obtained Ti₃AlC₂has a long-period multi-type structure of4H and cellparameters is a=b=3.0700and c=18.5456. The vickers hardness and compressivestrength of Ti₃AlC₂is3.74±0.09GPa and915±26MPa, respectively.The main intermediate phases were Al₃Ti, AlTi₃, TiAl, TiC, Ti₂AlC. Base on theresults of scanning electron microscopy （SEM） and transmission electron microscopy（TEM）, a possible reaction mechanism of Ti₃AlC₂fabricated by SPS is proposed. Resultsshow that AlTi₃and TiAl are main intermediate phases to form TiC and Ti₂AlC, thenTi₃AlC₂formed from the reaction between TiC and Ti₂AlC.The reaction mechanism of Ti₃AlC₂prepared by SPS is revealed as follows:Ti₅Si₃,SiC,Ti-Al intermetallic compounds and carbon reactions to form Ti₂Al_1-xSi_xC solidsolutions; then Ti₂Al_1-xSi_xC solid solutions and reactions to form Ti₃Al_1-xSi_xC₂solidsolutions.The lattice parameters c of the Ti₃Al_1-xSi_xC₂solid solutions decreases dramatically asthe Si content increases but lattice parameter a remains almost unchanged. Vickershardness and compressive strength of Ti₃Al_1-xSi_xC₂solid solutions increases as the Sicontent increases. The lattice parameters a and of Ti₃Al_0.73Si_0.27C₂is3.0716and18.2941。Vickers hardness and compressive strength of Ti₃Al_0.73Si_0.27C₂are enhanced30.6%and10.4%.