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, s tructure even for sizes smaller than 10 nm. The orientation relationships b etween the fine Cr particles and the Cu matrix were analyzed by observing M oire fringes. Two distinct orientation relationships were found: one close to the Kurdjumov-Sachs relationship and the other close to the Nishiyama-Wa ssermann relationship. The particles exhibited major facet planes: (533)(f) /(134)(b) for the Kurdjumov-Sachs particles and (533)(f)/(035)(b) for the N ishiyama-Wassermann particles. The relative stability of the two types of C r particles is discussed by adopting the invariant-line concept and the eig envectors of the transformation. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.