PREPARATION OF NITRIDES DISPERSED AL-TI ALLOY BY REACTIVE BALL-MILLING IN N-2 GAS

The nitride dispersed Al-Ti alloys have been prepared by reactive ball milling (RBM) of elemental powders of Al and Ti in nitrogen gas. XRD and TEM analyses showed that when Al-10, 20 wt. % Ti elemental powder mixtures were ball milled in nitrogen gas, no nitrides could be observ ed in Al-Ti alloy powders. In order to accelerate the formation of Ti nitrides, when only Ti powder was milled in nitrogen gas at the first stage and then a second stage milling was carried out with as-milled T i powder and elemental Al powder in the two-step RBM, TiN readily form ed and dispersed in the: Al matrix. The particle size and grain size w ere effectively reduced by the hard and brittle TiN and dissolved nitr ogen atoms. High resolution TEM analysis showed that the TiN, having t he grain size of 5 nm, existed between the Al matrix. The hardness of Al-Ti alloys milled in nitrogen gas was higher than that of Al-Ti allo ys milled in Ar gas. It seems that the TiN is an effective dispersion strengthener in Al-Ti alloys. After annealing treatment at 500 degrees C, the hardness of Al-Ti alloys hardly decreased with annealing time and they exhibited a good thermal stability. (C) 1998 Elsevier Science S.A. All rights reserved.