Atom-probe field-ion microscopy investigation of CMSX-4 Ni-base superalloy laser beam welds

CMSX-4 superalloy laser beam welds were investigated by transmission electron microscopy and atom probe field-ion microscopy(APFIM). The weld microstructure consisted of fine (10- to 50-nm) irregularly shaped gamma' precipitates (0.65 to 0.75 volume fraction) within the gamma matrix. APFIM compositions of the gamma and gamma' phases were found to be different from those in the base metal. Concentration profiles across the gamma and gamma' phases showed extensive variations of Cr, Co and Al concentrations as a function of distance within the gamma phase. Calculated lattice misfits near the gamma/gamma' interface in the welds are positive values compared to the negative values for base metal.