Study On The Fabrication Of Ti₂AlC Ceramic

New layered ternary Ti2AlC ceramic attracts increasing interest owing to its unique properties. TiiAlC 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. To date, many methods such as chemical vapor deposition (CVD), self-propagating high temperature reaction synthesis (SHS), hot pressing (HP),and hot-isostatic pressing (HIP) have been used for the synthesis of Ti2AlC. However, it is difficult to be synthesized as a pure phase, being often accompanied by unacceptably large amounts of TiC and titanium aluminium (Ti-Al) intermetallics So we conducted the research on the fabrication of single-phase TiaAlC material.In the present research, two series of raw materials (a) the elemental Ti, Al and C powders;(b) Ti,TiC,Al and C powders, were used to fabricate TiaAlC by spark plasma sintering and hot pressing respectively. In order to find the ideal synthesis conditions, different raw materials ratios in molar and various sintering temperatures were investigated. Additionally,effects of Si on the synthesis,and the crystal growth of Ti2AlC were especially studied. X-ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) were utilized to investigate the phase composition and the morphology characteristics of the products.In addition,someproperties of the pure Ti2AlC samples (density,Vickers hardness,and electrical conductivity) were measured respectively.Results indicated that fully dense,essentially single-phase Ti2AlC can be fabricated by spark plasma sintering (SPS) with 2Ti/1.2Al/C powder mixture at 1100℃ under 30 MPa soaking for 8 minutes. Its density is 4.10g/cm3, which is 99% theoretical density of TiiAlC. The obtained Ti2AlC grains are well developed and in plate-shape with a size of 8μm and 20μm in thickness and elongated dimension respectively. When using hot pressing method, high-purity dense Ti2AlC samples are obtained with raw materials molar ratio of n(Ti):n(Al):n(C)=2:1:1 at1500℃ under 30 MPa soaking for 1 hour. Also, nearly single-phase TiaAlC samples are prepared by hot pressing 1.5Ti/0.5TiC/1.0Al/0.5C powder mixtures at 1400℃ under 30 MPa soaking for 1 hour =Similar results were obtained in the research of effect of Si additive on the synthesis of high purity Ti2AlC in both spark plasma sintering and hot pressing methods no matter elemental powder mixtures or TiC were used as raw materials. That is: confined to our experimental conditions, Si additive enhances the synthesis of Ti3AlC2 instead of Ti2AlC. Si atoms enter the lattices of Ti3AlC2 and Ti2AlC to form solid solution respectively.