COHERENT SOLUBILITIES OF GAMMA' IN NI-AL NI-SI AND NI-TI ALLOYS

The coherent solubilities of the γ′ phase in Ni-Al, Ni-Si and Ni-Ti alloys have been determined from magnetic studies of γ′ particle coarsening and by electron metallographic observations. Over the temperature intervals 620-775°C (Ni-Al), 620-845°C (Ni-Si), and 525-775°C (Ni-Ti), the solubilities obey the empirical equations cAl = 0.2545 exp (-1418/RT)cSi = 0.2828 exp (-1768/RT)cTi = 0.2566 exp (-1850/RT) The solubilities above are expressed in terms of the atom fraction of solute in the saturated Ni-rich matrix and are estimated to be accurate to within ± 1%. These data are compared with literature values of the maximum solubilities of Al, Si and Ti in nickel. The data on γ′ in Ni-Al, in particular, are considered in light of a recent theoretical treatment of coherent two phase equilibrium by Oriani. It is concluded that previous investigators also determined the coherent solubility of γ′ in Ni-Al alloys. © 1969.