Synthesis of Ti4AIN3 and phase equilibria in the Ti-AI-N system

Abstract

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 isostatic pressing ("hipping") of A1N, TiN, and Ti or TiH2 powders at 1275 °C for 24 hours at 70 MPa. The pressed samples were further annealed under Ar for 168 hours at 1598 K, to obtain predominantly single-phase samples. 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 and to reflect the fact that Ti2AlN is in equilibrium with all the binary and ternary phases in the Ti-Al-N system except A1N.