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

A Ti-47Al-3Cr/Ti5Si3 composite with a submicrocrystalline structure was pro duced 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 ave rage grain size increased from 140 to 540 nm when the HIP temperature was i ncreased from 850 to 1050 degreesC. Grain growth in the composite in the te mperature 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-47 Al-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 right s reserved.