Al-Ni-Ti (Aluminium - Nitrogen - Titanium)

Abstract

Literature DataA critical assessment of the Al-N-Ti ternary system has been published by [1993Jeh], which included the literature data up to the year 1991. Thermodynamic data appearing up to 1997 are included in the thermodynamic assessment made by [1998Che]. Subsequently this system was investigated in different experimental approaches and for different temperatures. The present evaluation takes care of all data, from the first publication to the present. The investigations in this ternary system are concerned with (a) phase diagram studies, (b) preparation and characterization of the ternary compounds and (c) the formation of metastable solid solutions in the AlN-TiN pseudobinary system. The equilibria in the Ti-rich part of the ternary system have been determined by [1954Thy] for 0 to 10 mass% Al and 0 to 1 mass% N. This study applied micrograph analysis and X-ray diffraction of samples annealed at 600 to 1250°C, for 576 to 6 h. These samples were prepared from high purity arc molten alloys. The obtained results are given as vertical sections for constant N content. Annealing of Al-TiN bilayers on SiO 2 for 15 h at 645°C leads to the formation of AlN and Al 3 Ti, as the data of [1982Wit] show. These phases are also formed by reaction sintering of powder mixtures Al+TiN, containing 10, 15, 20 and 30 mol% TiN [1992Koy]. Titanium specimens with embedded AlN particles, as well as AlN-Ti and AlN-TiN diffusion couples were annealed at 900 to 1000°C up to 40 h by [2000Par]. It was shown that in AlN-TiAl diffusion couples a ternary Ti 2 AlN phase is formed at the interface. A more complex AlN-TiN-Ti 3 AlN-Ti 3 Al-Ti-Ti reaction zone was observed at the AlN-Ti interface. Thermodynamic calculations give the same sequence of expected layers between AlN and pure Ti [1998Lee] (the composition of Ti at the Ti 3 AlN/ Ti interface is close to the composition of Ti 3 Al). AlN never is in contact with Ti 3 AlN [2000Par]. Nitriding the intermetallic TiAl 3 in nitrogen and ammonium flow was studied by [1983Psh] in a temperature range of 600 to 1200°C. This work states that Al and Ti are nitrated in fact simultaneously, which results in formation of a heterogeneous mixture of practically not interacting binary nitrides. Experimental results imply that AlN-TiN, TiAl 3 -AlN and TiAl 3 -TiN are stable tie lines in the Al-N-Ti ternary system at low temperatures [1984Bey]. Phase equilibria in this ternary system were investigated at 1000 and 1300°C using previously prepared Al-Ti alloys, AlN, TiN and Ti powders [1984Sch]. About 30 ternary alloys were cold-pressed and sintered at the following conditions: 1000°C for 240 to 800 h in BN crucibles sealed in evacuated quartz tubes, 1200°C for 60 h in Mo crucibles under dynamic vacuum, 1300°C for 60 h in Mo crucibles under dynamic vacuum or for 50 h in BN (Mo) crucibles under argon and 1400°C in Mo crucibles under dynamic vacuum. As the alloys sintered at 1000°C were initially not in equilibrium they were powderized again, cold-pressed and sintered again. These two isothermal sections wer...