Recrystallization and aging effects associated with the high temperature deformation of waspaloy and inconel 718

Abstract

Cylindrical samples of Waspaloy and Inconel 718 were hot compressed, using a computerized Instron machine. The test program covered strain rates from 10•4 s•1 to 1 s•1 temperatures ranging from 875 °C to 1220 °C and deformations up to strains of 0.7. Interrupted tests were also carried out to determine the nature of the static softening and hardening processes. Dynamic recrystallization, partial or complete, was observed at temperatures above 950 °C. At 950 °C and below, dynamic recovery was the process controlling the deformation. Static softening was found to take place both by recovery and by recrystallization. Yield points were detected in Waspaloy under certain conditions as well as in Inconel 718. For Waspaloy the yield drops occurred in the vicinity of 1100 °C, and a deviation from the normal behavior in the stress-temperature curve was seen in the same temperature range. The mechanism responsible for the occurrence of the yield drops, which in turn is related to the deviation in the σvsT curve, is believed to be short range ordering of the γ’ forming elements. For Inconel 718, elements such as Co, Cr and Fe may be causing short range ordering, but the locking mechanism may also be associated with the precipitation of carbides or other intermetallic phases on the dislocations.