Synthesis and mechanical properties of Ti 3AlC 2 by hot pressing TiC x/Al powder mixture

Abstract

A study has been performed to synthesize polycrystalline bulk Ti 3AlC 2 by hot pressing from TiC x ( x = 0.6) and Al powder mixture at the temperature range of 800–1600 °C under 25 MPa for various times. Relatively pure Ti 3AlC 2 was successfully synthesized above 900 °C. Small amount of Ti 2AlC as a secondary phase was observed along with Ti 3AlC 2 below 1400 °C. With increasing hot pressing time to 1250 °C, the amount of un-reacted TiC x was gradually decreased while Ti 3AlC 2 was appeared to be a dominant phase. The densification of Ti 3AlC 2 was examined as a function of hot pressing temperature up to 1600 °C as well as it was investigated with hot pressing time at 1250 °C. Near fully dense Ti 3AlC 2 was synthesized as the hot pressing time was increased at 1250 °C. Fully dense and pure Ti 3AlC 2 could be synthesized by hot pressing above 1400 °C. The resulting Ti 3AlC 2 above 1400 °C showed the typical laminated and platelet grain structure of ternary carbides. With increasing processing temperature to 1600 °C, the typical platelet grain structure of Ti 3AlC 2 was started to be destroyed and significant grain coarsening was occurred, which might be caused by partial melting of Ti 3AlC 2. The Vickers hardness of bulk Ti 3AlC 2 was about 3.5–6 GPa under the loading of 10 N. The maximum flexural strength of synthesized bulk Ti 3AlC 2 was over 900 MPa. The new process using TiC x /Al powder mixture as a starting material made it possible to shorten the synthesis time, to reduce processing temperature, as well as to improve the flexural strength of Ti 3AlC 2.