Constitutive Equation for AISI4140 Steel Applicable to a Wide Range of Strain Rates at Elevated Temperatures

Abstract

This paper presents a method to determine a constitutive equation of AISI4140 steel when it deforms at a wide range of strain rates (0.05~1900s−1) under high temperatures. The fundamental idea considered here is that the dependency of flow stress upon strain rate and temperature is described by the power law model of the Arrhenius equation. Strengthening coefficient and work hardening exponent are introduced to take a simplified treatment to the flow stress behaviour characteristics without losing accuracy of the model. The validity of the proposed constitutive equation has been examined using results obtained from the hot compression test (GLEEBLE® 3500C) and Split Hopkinson‐Pressure Bar test at high temperature. Results revealed the proposed constitutive equation could predict flow stress‐strain curve of the steel with an acceptable amount of error at the ranges of strain rates.

Room temperature nanoindentation creep of nitrocarburised AISI 4140 steel

“…Das et al [8] discussed the room temperature creep behaviour of different regions of the heat-affected zones of 9Cr-1Mo steel weldments, Ghassemi-Armaki et al [9] conducted nanoindentation to obtain the micromechanical response of the individual ferrite and martensite, Zhu et al [10] investigated the room temperature nanoindentation creep of nanoscale Ag/ Fe multilayers. Certainly, there are some research studies on the integral mechanical properties of AISI 4140 steel and nitrided steels [13][14][15], while few experimental works on the room temperature creep behaviour of the individual zone of nitrocarburised AISI 4140 steel have been performed to study the connections of the nitrocarburising process, the microstructures and the creep behaviours, and to obtain the room temperature creep deformation mechanisms of nitrocarburised steel.…”

“…[10] investigated the room temperature nanoindentation creep of nanoscale Ag/Fe multilayers. Certainly, there are some research studies on the integral mechanical properties of AISI 4140 steel and nitrided steels [13-15], while few experimental works on the room temperature creep behaviour of the individual zone of nitrocarburised AISI 4140 steel have been performed to study the connections of the nitrocarburising process, the microstructures and the creep behaviours, and to obtain the room temperature creep deformation mechanisms of nitrocarburised steel.…”