Grain growth in ultrafine titanium powders during sintering

Grain growth behaviour of fine (3 μm) and attrition milled nanocrystalline (32 nm) titanium powers during sintering have been studied. The activation energies of grain growth (Q ^sub g^) in fine titanium were found to be 192.9 and 142.4 kJ/mol at lower and higher temperature ranges, respectively. The nanocrystalline titanium showed very low values of Q ^sub g^ (54.6 kJ/mol) at lower temperatures and it increased to 273.2 kJ/mol at higher temperatures. The constant (n) in nano Ti system was found to have unusually very high values of 6.5-8.2. The grain boundary rotation along with the diffusional processes could be the grain growth mechanism in nanocrystalline and in fine titanium powders.[PUBLICATION ABSTRACT]