Characterization of the microstructure evolution in a nickel base superalloy during continuous cooling conditions

The solidification characteristics of the gamma -phase from the liquid and the subsequent decomposition of the gamma phase control the evolution of th e microstructure in nickel-base superalloy welds. The precipitation of the gamma phase from the gamma phase during continuous cooling conditions (0.17 -75 K s(-1)) from the solutionizing temperature was characterized in a dire ctionally solidified CM247DS alloy with thermomechanical simulator, and by transmission electron microscopy, atom probe field ion microscopy and atom probe tomography. The number density increased; size decreased and morpholo gy of the gamma precipitates changed with an increase in cooling rate. Unde r rapid water-quenched conditions. complex partitioning of the alloying ele ments between gamma and gamma phases was observed, Atom probe tomography on samples subjected to slower cooling rates showed different partitioning be havior compared to that of water-quenched samples and the presence of secon dary gamma precipitates in the samples subjected to a cooling rate of 1 K s (-1). Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.