Atomic structure of the Cu precipitates in two stages hardening in Maraging steel

Fine precipitates in 15-5 PH Maraging steel in two stages hardening were analyzed by transmission electron microscopy. HREM observation reveals the formation of the fine precipitates (4-12 nm) with a 9R structure, after aging at 480 degrees C for 2 h. A second type of copper precipitate with a f.c.c. structure, spherical in shape, was observed on aging at 650 degrees C. The spherical copper precipitates are thought to grow by the mechanism of moving steps. (c) 2005 Elsevier B.V. All rights reserved.