Solid-liquid reaction synthesis of layered machinable Ti3AlC2 ceramic

Fully dense polycrystalline Ti3AlC2 was fabricated by a solid-liquid reaction synthesis and simultaneous in-situ hot pressing of a mixture of Ti, Al and graphite powders at 1500 degreesC and 25 MPa for 5 minutes and subsequently annealing at 1200 degreesC for 20 minutes. The effects of various parameters including composition of the initial elemental powders, temperature as well as the hot pressing pressure on the purity, formation and densification of Ti3AlC2 were examined. In addition, the reaction path for the formation of Ti3AlC2 was investigated by DTA, XRD, SEM and EDS, suggesting that the reaction path during the heating process could be reasonably described as follows: Al powder melted at some 660 degreesC and coated the Ti particles; at about 740 degreesC the exothermic reactions between Al and Ti occurred and Ti-Al intermetallics like TiAl and Ti3Al were formed; the diffusion of carbon in the Ti-Al intermetallics at elevated temperature resulted in the carbides Ti2AlC, Ti3AlC and TiC; and finally these carbides and the unreacted graphite reacted at about 1420 degreesC to yield Ti3AlC2.