Preparation of nitrides dispersed Al-Ti alloy by reactive ball milling in N2 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 observed 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 Ti powder and elemental Al powder in the two-step RBM, TiN readily formed and dispersed in the: Al matrix. The particle size and grain size were effectively reduced by the hard and brittle TiN and dissolved nitrogen atoms. High resolution TEM analysis showed that the TiN, having the 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 alloys 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.