A number of nickel based alloys, conventional cast and wrought, powder consolidated and oxide dispersion strengthened materials, have shown a superplastic behaviour when thermomechanically processed to a fine grain microstructure. In this paper a simple thermal and mechanical treatment to obtain the microstructural prerequisites for superplastic behaviour of IN-718 superalloy is reported. The processing route includes a high-temperature solution treatment, water quenching and cold rolling. The heavily rolled microstructure dynamically recrystallizes to a very fine microstructure during the early stages of superplastic deformation. When the alloy was deformed at temperatures between 900 °C and 980 °C, with strain rates ranging from 2.42·10-4 s-1 to 4.8·10-3 s-1, elongations always higher than 300% were obtained. A maximum elongation to failure of 1050% was measured in the specimen deformed at 920 °C and with a strain rate of 9.68·10-4 s-1. The influence of the microstructural parameters (grain size and volume fractions of the γ and δ (Ni3Nb) phases) on superplastic properties is discussed.
Superplastic behaviour of fine-grained IN-718 superalloy
GARAGNANI, Gian Luca;
1994
Abstract
A number of nickel based alloys, conventional cast and wrought, powder consolidated and oxide dispersion strengthened materials, have shown a superplastic behaviour when thermomechanically processed to a fine grain microstructure. In this paper a simple thermal and mechanical treatment to obtain the microstructural prerequisites for superplastic behaviour of IN-718 superalloy is reported. The processing route includes a high-temperature solution treatment, water quenching and cold rolling. The heavily rolled microstructure dynamically recrystallizes to a very fine microstructure during the early stages of superplastic deformation. When the alloy was deformed at temperatures between 900 °C and 980 °C, with strain rates ranging from 2.42·10-4 s-1 to 4.8·10-3 s-1, elongations always higher than 300% were obtained. A maximum elongation to failure of 1050% was measured in the specimen deformed at 920 °C and with a strain rate of 9.68·10-4 s-1. The influence of the microstructural parameters (grain size and volume fractions of the γ and δ (Ni3Nb) phases) on superplastic properties is discussed.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
