INVESTIGATION OF EQUILIBRIUM AND PHASE-STABILITY IN THE LIQUID-SOLID STATE IN NICKEL-BASED WROUGHT SUPERALLOYS

Isothermal holding experiments between the liquidus temperatures, T-L, and the solidus temperatures, T-S, were carried out on nickel-based w rought superalloys. It was found that during solidification the elemen ts aluminium, cobalt and tungsten tend to dissolve in the gamma matrix whereas titanium, tantalum and molybdenum tend to segregate into the liquid. Molybdenum and titanium cause the formation of brittle sigma a nd eta phases, respectively, after prolonged holding at elevated tempe ratures, in accordance with the results of New-PHACOMP (new phase comp utation).