Synthesis of Nanograined Ti-Al-Cr-Nb-X [X = Ni-P-Coated Graphite and Carbon] Intermetallic Matrix Composites by Mechanical Alloying

Abstract

In the present work, TiAl-based intermetallic matrix composite with second phase reinforcement as Ni-P-coated carbon and graphite powders were synthesized by mechanical alloying route. Graphite powder (20–30 µm) and elemental carbon powders (1–5 µm) were coated with Ni-P by the electroless coating technique, which was added to the elemental powder mixtures of Ti-48Al-1%Cr -1%Nb with 1% composition of either of the two. The powder mixtures were subjected to mechanical alloying at 300 rpm up to 250 h using toluene as a process control agent. The samples were collected after 25 h duration and characterized. The formation of TiAl (γ) and Ti3Al (α 2) phases are confirmed by x-ray diffraction. The formations of these phases were found after milling for 75 h in case of graphite addition and 100 h in case of carbon addition in the intermetallic matrix. The mechanically alloyed samples milled for different extents of time were examined by a field emission scanning electron microscope (FESEM) and energy dispersive x-ray (EDAX) spectroscopy; the grain size was determined to be in the size range of 140–189 nm for the mechanically alloyed mixture.