Structure and properties of nanocrystalline TiC full-density bulk alloy consolidated from mechanically reacted powders

High-energy bah milling has been successfully employed for synthesizing nanocrystalline powders of Ti44C56. The milling procedure involves milling of elemental Ti and C powders at room temperature in an argon gas atmosphere. The progress of the mechanically induced solid state reaction was monitored by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy and/or high resolution transmission electron microscopy at several stages of the milling time. A single phase of NaCl-type TiC is obtained after 22 ks of milling time. No free Ti and/or C crystals could be detected at this stage of milling. Increasing the milling time leads to a decrease in the grain size of the powders to <50 nm in diameter after 40 ks of milling time. Towards the end of the milling processing time (720 ks) the powders possess excellent morphological characteristics, such as a homogeneous shape (spherical-like morphology) with fine and smooth surface relief and uniform size (<1 mu m in diameter). The lattice parameter of this end-product was calculated to be 0.4326 nm. In addition, the powders at this final stage of milling consist of nanocrystalline grains (<5 nm in diameter) with cell-like morphology. In order to determine some physical and mechanical properties of the synthesized TiC material, different samples at different milling times were consolidated into bulk samples, using a plasma activated sintering method. The powders of the final-product (720 ks) has a density of 5.21 g/cm(3), being nearly the theoretical density of TiC. In addition, this bulk sample maintains its unique structure characteristics with nanocrystalline grains of <60 nm in diameter. On the basis of the results of the present study, the ball-milling technique accompanied with plasma activated sintering can provide powerful tools for the fabrication of nanocrystalline TiC bulk alloys with unique and advanced properties. (C) 2000 Elsevier Science S.A. All rights reserved.