Synthesis of Ti4AlN3 and phase equilibria in the Ti-Al-N system

Recently, we have shown that the ternary originally thought to be Ti3Al2N2 was Ti4AlN3.([1]) In this work, polycrystalline, fully dense, predominantly single-phase bulk samples of Ti4AlN3-x were fabricated by reactive hot iso static pressing ("hipping") of AlN, TiN, and Ti or TiH2 powders at 1275 deg rees C for 24 hours at 70 MPa. The pressed samples were further annealed un der Ar for 168 hours at 1598 K, to obtain predominantly single-phase sample s. The current Ti-Al-N isothermal (1598 K) phase diagram, based on Ti3Al2N2 , has been revised to take into account the presence of Ti4AlN3-x instead a nd to reflect the fact that Ti2AlN is in equilibrium with all the binary an d ternary phases in the Ti-Al-N system except AlN.