HIGH-RESOLUTION MICROSTRUCTURE ANALYSIS OF THE DECOMPOSITION OF CU90CO10 ALLOYS

Homogeneous Cu-Co alloys with a Co concentration up to 10 at.% Co are prepared by rapid quenching. This allows for the first time the invest igation of the decomposition process of the Cu90Co10 supersaturated so lid solution on a nanometer scale using a combination of atom probe/fi eld ion microscopy (AP/FIM) analyses and transmission electron microsc opy. Annealing of a Cu(90)Co(10) alloy at 440 degrees C for various ti mes leads to a compositional modulated microstructure. The composition profiles determined by AP/FIM analyses clearly exclude a classical nu cleation and growth behavior and instead suggest a spinodal type decom position whereby the compositions of the precipitates continuously inc rease. In contrast, at the grain boundaries of the Cu90Co(10) alloy he terogeneous nucleation of pure Co particles is observed.