Synthesis and characterization of a TiAl/Ti5Si3 composite with a submicrocrystalline structure

A Ti-47Al-3Cr/Ti5Si3 composite with a submicrocrystalline structure was produced by mechanical alloying (MA) and hot isostatic pressing (HIP). Blends of elemental and pre-alloyed powders were used for the MA, Intimate mixing of the elements and powder amorphization occurred during MA. HIP of the MA powder resulted in a fully dense material with a submicron grain size and a homogeneously distributed mixture of gamma-TiAl and Ti5Si3 grains. The average grain size increased from 140 to 540 nm when the HIP temperature was increased from 850 to 1050 degreesC. Grain growth in the composite in the temperature range 850-1100 degreesC was described by the equation D-4 - D-o(4) = K-o exp(- Q/RT)t where Q = 330 kJ mol(-1) and K-o = 3.0 x 10(-18) m(4) s(-1). The kinetic behavior was similar to that for a nanocrystalline Ti-47Al-3Cr alloy annealed in the same temperature range, i.e. the Ti5Si3 phase had little effect on grain growth. (C) 2001 Elsevier Science B.V. All rights reserved.