Grain sizes were measured in bulk nanocrystalline copper processed by inert gas condensation and compaction, using X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods. The XRD peaks were analyzed using the Warren-Averbach, integral breadth and Williamson-Hall methods, modified to include the contributions of dislocations to peak broadening. Analysis using full-width half-maximum values provided the largest average grain sizes, while analyses of integral breadth and Fourier coefficients of XRD peak profiles gave the medium and smallest average grain sizes, respectively. A significant increase in the mean grain size accompanied by broadening of the grain size distribution could be observed upon increasing the temperature of compaction of nano-powders from 69°C (342 K = 0.25TM) to 180°C (453 K = 0.34TM) or after a six-month exposure of samples to ambient temperatures (TM is the absolute temperature of melting). Grain size distributions, obtained by direct measurement of the dimensions of ∼500 grains per sample using bright and dark field transmission electron microscopy, were found to obey a log normal relationship. The TEM results agreed well with those of XRD measurements for narrow grain size distributions with smaller mean values, but they deviated significantly when the mean grain size increased and distributions widened, indicating that the information from XRD analyses could be misleading.
|Number of pages||8|
|Journal||Transactions of the Indian Institute of Metals|
|Publication status||Published - Dec 1 2005|
ASJC Scopus subject areas
- Metals and Alloys