Dynamic recrystallization behavior and constitutive analysis of Incoloy 901 under hot working condition

Hot deformation behavior of Incoloy 901 Ni-based superalloy was investigated by performing hot compression tests over the temperature range of 950-1100 degrees C and at strain rates of 0.001-1 s(-1). The flow curves at low strain rates i.e. 0.001-0.1 s(-1), were characterized by a faint peak or a long plateau after the work hardening region. Only at high strain rates, e.g. 1 s(-1), the flow curves exhibited sharp peaks of dynamic recrystallization. The strain associated with the peak points of flow curves firstly increases with strain rate (up to 0.01 s(-1)) and then unexpectedly decreased at higher strain rates. These anomalous results were attributed to the change in the kinetics of dynamic softening mechanisms. The constitutive analysis of flow stress suggested a change in the hot deformation behavior of the alloy with increasing temperature (over 1050 degrees C) or strain rate (over 0.01 s(-1)). Microstructural characterization showed that although dynamic recrystallization would operate over the whole studied ranges of deformation temperature and strain rate, its kinetics was generally sluggish. However, the rate of recrystallization increased remarkably at temperatures beyond 1050 degrees C or strain rate over 0.01 s(-1). Electron backscattered diffraction (EBSD) measurements and optical microscopy observations showed that the nucleation of recrystallization around the grain boundaries or second-phase particles should be due to the gradual evolution of subgrains. (C) 2014 Elsevier B.V. All rights reserved.