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°C. Grain growth in the composite in the temperature range 850–1100°C was described by the equation D4−Do4=Ko exp(−Q/RT)t where Q=330 kJ mol−1 and Ko=3.0×10−18 m4 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.