Stability of Titanium-aluminium Nitride （Ti_2AlN） at High Pressure and High Temperatures

The stability of Ti2AlN at high pressure of 5 GPa and different temperatures of 700-1 600 ℃ was investigated using X-ray diffraction （XRD）,scanning electron microscopy （SEM） equipped with an energy dispersive spectrometer （EDS）.Ti2AlN was found to be stable at temperatures as high as 1 400 ℃under 5 GPa for 20 min,and was proved that it held better structure stability than Ti2AlC under 5 GPa through comparative experiments of Ti2AlN and Ti2AlC （representative compounds of M2AX phases （211 phase））.The reaction process at high pressure had some difference from that at ambient pressure/vacuum,and Ti2AlN directly decomposed to TiN and TiAl at 5 GPa and 1 500 ℃ for 20 min.Moreover,the mechanism of phase segregation was discussed.In addition,the behavior of Ti2AlN contacting with Zr at high pressure and high temperature （HPHT） was also studied.