300M steel is a typical ultra-high strength steel with very high strength, excellent fracture toughness, good fatigue strength and stress corrosion resistance, and thus it has found expansive applications in the manufacture of key components of military and civil aircrafts.
300M steel can be formed into complex-shaped parts such as landing gears which are one of the four core components of aircraft, as well as into sheet or rod. However, deformation of 300M steel should be performed at elevated temperatures because of its high strength and limited ductility.
In recent years, some scholars have established constitutive models to predict the hot deformation behavior in ultra-high strength steels. Unfortunately, few studies on phenomenological models for 300M steel have been conducted or reported, except for the AT model.
Sim Kyong Ho, a researcher at the Faculty of Materials Science and Technology, has developed and improved sc-AT, m-JC and KHL models to describe the hot deformation behavior of 300M ultra-high strength steel.
First, he conducted isothermal uniaxial compression tests under various thermo-mechanical processing conditions.
Second, by using the experimental data, he developed the AT, m-JC and KHL models for 300M steel, and evaluated the predictability of the models.
Based on the analysis of the cause of large deviation, he further improved the m-JC and KHL models, and verified the prediction accuracy of the five constitutive models by using standard statistical parameters.
He drew the following conclusions.
The m-JC and KHL models show relatively good predictability at the reference conditions. The sc-AT model exhibits the highest R2 value of 0.9971 and the lowest AARE value of 3.57 %. In view of the prediction accuracy and computation complexity, the improved versions of m-JC and KHL models are preferred models among the phenomenological constitutive models he studied.
The details are found in his paper “Development and Improvement of Several Phenomenological Constitutive Models for Thermo-mechanical Processing of 300M Ultra-high Strength Steel” in “Journal of Materials Engineering and Performance” (SCI).
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