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 e lectron microscopy and atom probe field-ion microscopy(APFIM). The wel d microstructure consisted of fine (10- to 50-nm) irregularly shaped g amma' precipitates (0.65 to 0.75 volume fraction) within the gamma mat rix. APFIM compositions of the gamma and gamma' phases were found to b e different from those in the base metal. Concentration profiles acros s the gamma and gamma' phases showed extensive variations of Cr, Co an d Al concentrations as a function of distance within the gamma phase. Calculated lattice misfits near the gamma/gamma' interface in the weld s are positive values compared to the negative values for base metal.