CLASSICAL PRECIPITATION DYNAMIC MODEL OF γ′ PHASE OF NICKEL-BASED SUPER ALLOYS AND APPLICATIONS

Based on the classical nucleation theory, and considering the effects of heat temperature and preservation time on precipitation, the gamma' precipitation model in nickel-based superalloy was established. In combination with the characteristic value data of gamma' precipitation which was got by isothermal aging experiment of GH738 alloy, the relative accuracy of simulation result was verified. Results show that the classic dynamic model of the precipitation can better forecast that gamma' phase of multiple complex nickel-based alloy system mainly precipitate by uniform nucleation. Further, precipitation model was combined with four typical superalloys GH80A, GH738, U720Li and DD407. The effects of the contents of Al, Ti and its ratio change on the precipitation of gamma' were calculated and analyzed. Results showed that the better role of Al than Ti on equilibrium content. Under the premise of equal amount of Al + Ti, the increasing of Ti had a greater contribution to the driving force of precipitation and complete precipitation time, and increased the volume fraction of the beginning of precipitation, but reduced the size of precipitated phase.