Preparation Of TiC_x By Mechanical Alloying And Compositing With Second Phase

TiC possesses many excellent physical and chemical properties, Nevertheless, thehigh melting point and difficulty for sintering limit its application. In this experiment, Thenonstoichiometric TiC(TiCx) powders are fabricated by means of mechanical alloying(MA)synthesis method, in addition, atoms diffuse in the interface region of two phase by highpressure sintering, Which can reduce the sintering temperature to optimize properties ofbulk materials.In the experiment Ti powder and TiC powder in accordance with Ti, C molar massratio1:0.3,1:0.4,1:0.5(respectively code TC3, TC4, TC5) synthetic nonstoichiometricTiCx by mechanical alloying (MA). An X-ray diffractometer (XRD) and a sanningelectron microscope (SEM) are used to analyze the structures and observe themorphologies of the milled powders. The grain size is up to8nm and a particle size isabout50-100nm. All specimens are heated in a vacuum furnace at600℃and800℃.α-Ti(C) diffraction peak and TiC diffraction peak appear in the XRD of TC3powdersafter600℃annealing.After TiCx (MA) sintered under the high temperature and high pressure, some TiCxtransform into hexagonal structure compound. The carbon content of the compounddeviates from Ti6C3.75, which reveals the compound is hexagonal structurenonstoichiometric TiC compound. With increase of carbon content and milling timeprolonged, the content of hexagonal compound reduce or even disappear afterhigh-pressure sintering. TiCx powder annealed at800℃sinter at high pressure. All ofTiCx maintain face-centered cubic structure. TiCx powder annealed at600℃sinter athigh temperature of1200-1500℃and pressure of5.5GPa for5min. The fracturesurfaces of the sintered samples are investigated by SEM and the mechanical propertiesare tested. At1200℃, grain size of TC3sintered samples is fine. the hardness andtoughness of TC3reached15.17GPa and5.57MPa·m1/2, respectively. at the same time,grain size of TC4sintered samples is fine. the hardness and toughness of TC4reached25.5GPa and3.74MPa·m1/2, respectively. Layered or mixed powder of TC4/AlN sinter at temperature of1500℃and highpressure of5.5GPa for5min. block composite material are analysised by a sanningelectron microscope (SEM) on the morphology analysis and spectroscopy for elementalanalysis. In TC4/AlN sintered interface, The Al and N atom diffuse from AlN to TC4through the vacancy diffusion mechanism. There is a similar diffusion phenomenon inTC4/AlN mixed powder sintering.Mechanical properties of7:3volume ratio of the TC4/AlN sintered body is better at1500℃. Its toughness value is71%higher than that of single phase TC4and its hardnessvalue is decreased by10.2%. During different proportions of TC4/AlN Sintering, with theincrease in the proportion of TC4, the hardness is bigger and the toughness is almostconstant when the proportion of TC4/AlN is8:2, AlN is almost completely decomposed.toughness values is54%higher than that of single phase TC4and the hardness isdecreased by5.5%.