Investigation of metastable gamma ' precipitate using HRTEM in aged Cu-Be alloy

Plate-like precipitates in Cu-1.9Be alloy have been studied using high-resolution transmission electron microscopy (HRTEM). The metastable gamma' phase and its matrix orientation were determined in samples which were solutionized, after aging at 320 degrees C for 2, 6 and 72 h. The relationships were determined as follows: [0 1 1] Cu-matrix (alpha)//[0 0 1] precipitate (gamma') and (1 0 0)alpha//(1 0 0)gamma'. The habit planes were determined to be the (3 1 (1) over bar) and ((2) over bar 1 (1) over bar) planes of a for the gamma' phase. The angle between [1 0 0]gamma' and [2 0 0]alpha was found to be 6 degrees and 6.5 degrees for aging times of 6 h and 72 h, respectively. As the aging time increased, the length and width of the Cu-Be precipitates increased from 10-20 nm to 50-100 nm and 2-5 nm to 10 nm, respectively, along the trace of the habit planes. (C) 2011 Elsevier B.V. All rights reserved.