Crystallography and morphology of nanosized Cr particles in a Cu-0.2% Cr alloy

The crystallography and morphology of nanosized Cr precipitate particles in a Cu matrix have been examined using an aged Cu-0.20 mass% Cr alloy at 773 K. By HRTEM observations, the Cr particles were found to have the b.c.c, structure even for sizes smaller than 10 nm. The orientation relationships between the fine Cr particles and the Cu matrix were analyzed by observing Moire fringes. Two distinct orientation relationships were found: one close to the Kurdjumov-Sachs relationship and the other close to the Nishiyama-Wassermann relationship. The particles exhibited major facet planes: (533)(f)/(134)(b) for the Kurdjumov-Sachs particles and (533)(f)/(035)(b) for the Nishiyama-Wassermann particles. The relative stability of the two types of Cr particles is discussed by adopting the invariant-line concept and the eigenvectors of the transformation. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.