High-Temperature Plastic Flow of Haynes 282 Under Continuous-Heating Conditions

The interaction of plastic flow and microstructure evolution during continuous heating of superalloy Haynes 282 sheet was quantified using constant-stress, constant-heating-rate (CSCHR) tests coupled with simulations of precipitation and dissolution. Prior to deformation, sheet samples were supersolvus solution treated and furnace cooled or oil quenched, thereby producing a microstructure comprising equiaxed γ grains with or without γ′ precipitates, respectively. CSCHR test parameters consisted of stresses in the range of 121 to 414 MPa and heating rates of 75 or 28 °C/min. In all cases, plastic flow was characterized by a strain rate which increased with temperature. The Arrhenius plots derived from such measurements showed nearly-linear or bi-linear behaviors whose slopes increased with temperature below the nominal equilibrium γ′ solvus and then decreased above the solvus. The effect of dislocation-precipitate interactions on plastic flow was quantified using precipitation/dissolution simulations and estimates of the instantaneous threshold stress derived from comparisons of Arrhenius plots for single-phase and two-phase behaviors. Such comparisons revealed that plastic-flow was limited by the climb of dislocations over the γ′ precipitates.