Phase transformations in a Cu-35 at.% Mn-25 at.% Al alloy

The phase transformations in the Cu-35 at.% Mn-25 at.% Al alloy have been investigated by means of transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDS). In as-quenched condition, the microstructure of the alloy was a mixture of (L2(1)+B2+L-J) phases. This is different from that observed by previous workers in the Cu3-xMnxAl alloys with x <= 1.0. When the as-quenched alloy was aged at 460 degrees C for short times, gamma-brass precipitates started to occur at anti-phase boundaries (APBs). After prolonged aging at 460 degrees C, the gamma-brass precipitates grew and beta-Mn precipitates were formed at the regions contiguous to the gamma-brass precipitates. The coexistence of (gamma-brass + beta-Mn) has never been observed by previous workers in Cu-Mn-Al alloy systems before. (c) 2005 Elsevier B.V. All rights reserved.