Dynamic recrystallization of a new nickel-based alloy for 700 °C A-USC power plant applications with different initial states: as-homogenized and as-forged

The hot deformation behavior of a new-designed nickel-based alloy with different initial states were investigated by isothermal compression at temperature range of 1000-1200 degrees C with strain rate of 0.01-20 s(-1) and nominal strain of 15-70% on a Gleeble-1500 thermo-mechanical simulator. The correlation of dynamic recrystallization (DRX) mechanism and initial alloy states as well as deformation parameters were analyzed in detail by means of transmission electron microscope (TEM) and electron backscattered diffraction (EBSD). For homogenized alloy with extremely large grains, the DRX mechanism transforms partly from discontinuous dynamic recrystallization (DDRX) characterized with serrated and bulging grain boundary into continuous dynamic recrystallization (CDRX) operated by progressive sub-grain merging and rotation with the increasing strain rate and decreasing deformation temperature, which results from the poor deformation compatibility in the alloy with extremely large grains. However, the dominant DRX mechanism in as-forged alloy is DDRX almost at all the deformation conditions, and CDRX is only an assistant mechanism, which caused by the initial inhomogeneous dislocation distribution and fine grains. In consequence, the initial alloy states have a significant influence on the DRX, which cannot be ignored in the hot deformation research. (C) 2016 Elsevier B.V. All rights reserved.