ATOMIC-SCALE INVESTIGATION OF GRAIN-BOUNDARY MICROCHEMISTRY IN THE NICKEL-BASED SUPERALLOY ASTROLOY WITH A 3-DIMENSIONAL ATOM-PROBE

A new three-dimensional (3D) atom probe was used to study grain-bounda ry segregation and ordering phenomena in a two-phase (gamma-gamma') Ni -based superalloy, namely Astroloy. The tomographic images show that t he grain-boundary serration is due to gamma' precipitates which develo p along boundaries during cooling. These 3D reconstructions also exhib it segregations of B, C, Mo and Cr at grain boundaries. They also reve al that the degree of order in gamma' particles which are located alon g boundaries is preserved up to the grain boundary.