Tensile properties of nitride dispersed Al-Ti alloy synthesized by reactive ball milling in N-2 gas

Nitride dispersed Al-Ti alloys have been prepared by reactive ball milling (RBM) of elemental powders of Al and Ti in nitrogen gas. The particle size and the grain size were effectively reduced by the hard and brittle TiN and the dissolved nitrogen atoms. The as-milled powder was consolidated by hot extrusion at 500 degrees C. The grain size of the as-extruded specimen was about 50-100 nm, and TiN with a grain size of 10 nm existed all over the s pecimen. UTS of Al-10 wt.%(Ti+TiN) alloy produced by two-step RBM in N-2 an d hot extrusion was lower than that of Al-5 at.%Ti alloy prepared by RBM in H-2 and hot extrusion, although the hardness of the former was higher than that of the latter. The ductilities of Al-10 wt.%(Ti+TiN) were very poor a nd even less than those of specimens prepared by RBM in H-2. The dispersoid s existing at the grain boundary appeared to restrict deformation through t he grain boundary and promote the formation of micro-voids at the grain bou ndaries. Thus, fracture easily occurred intergranularly in this ahoy and th e ductility was poor at all tested temperatures. (C) 2000 Elsevier Science S.A. All rights reserved.