Three-dimensional atom probing of supersaturated mechanically alloyed Cu–20at.% Co

Cu–20at.% Co was mechanically alloyed from pure elements by ball milling for 28 h. The powder was compacted into pellets at room temperature by applying a pressure of 0.5 GPa. Microstructural investigations were carried out by three-dimensional atom probing (3DAP) after annealing at 400 °C for 2 h in Ar atmosphere. The annealed Cu–20at.% Co exhibits a heterogeneous microstructure. Cu-rich and Co-rich particles with 8.7 at.% Co and 1.3 at.% Cu, respectively, and highly supersaturated regions with average Co concentrations between 25 and 35 at.% were detected. A new, sensitive statistical analysis of the 3DAP data obtained from a supersaturated region revealed concentration fluctuations of ±24 at.% Co with an average wave length of about 2 nm indicating spinodal decomposition.