a1 Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, 721302 India
This work represents an attempt to understand the nature of micron and attrition milled nano-sized titanium powders on two different aspects, i.e., pressure-induced phase change and thermal expansion. Contraction in the volume of unit cell in terms of decrease in interplaner spacing (d) has been observed in both powders and tends to restore upon annealing. At a given pressure, nano titanium shows a smaller decrease in d relative to micron titanium. The stress analysis of the compacts indicates higher value of residual stresses and deformations in micron powder than in nano powder. The dilatometric study reveals, first, the release of internal stresses and entrapped gases causes huge expansion in nanopowder compacts during heating. Secondly, there is no significant difference in the expansion coefficients of sintered micro- and nanocrystalline titanium samples.
(Received August 24 2004)
(Accepted October 12 2004)
(Online publication March 2005)