Effects of strain rate and temperature on deformation behaviour of IN 718 during high temperature deformation

Abstract

The hot deformation characteristics of a wrought IN 718 alloy were investigated by compression testing at constant strain rates in the range of 0.1 to 5 × 10 −3 s −1, and testing temperatures in the range of 950 to 1100 °C using a 200 ton capacity microprocessor controlled Fielding hydraulic press. Examination of the microstructures was carried out by optical microscopy and TEM. The flow stress of the compression tests showed a single peak in the flow stress-strain curves, and indicated that a dynamic recrystallization transition took place during the hot compression. The relationship between the peak stresses (σ p) and the Zener-Hollomon parameter ( z) can be expressed by σ p = 0.5Z 0.17. “Necklace” microstructures were observed at testing temperatures below 1050 °C, for strain of 0.7. The fraction of recrystallized grains increased with the increasing temperature and strain, and decreasing strain rate. Fully recrystallized microstructures were observed at temperatures 1050 °C or greater, with a strain of 0.7.