Nanocrystalline samples, with grain sizes ranging from 12 to 94nm, were synthesized by crystallizing an amorphous alloy. High-resolution electron microscopy revealed that the nanocrystalline samples comprised many so-called orientation regions. Each such region consisted of a high density of well-defined micro-twin domains. Positron annihilation spectroscopy showed that 2 types of defect were present. Upon increasing the annealing temperature to 973K, the 2 types of defect underwent considerable change whereas the micro-hardness changed only slightly.

X.D.Liu, M.Umemoto, W.Deng, L.Y.Xiong, D.H.Ping, K.Lu: Journal of Applied Physics, 1997, 81[3], 1103-8