In-Situ Neutron Diffraction and Crystal Plasticity Finite Element Modeling to study the Kinematic Stability of Retained Austenite in Bearing Steels

TL;DR

This study combines in-situ neutron diffraction and crystal plasticity finite element modeling to accurately analyze the kinematic stability and transformation behavior of retained austenite in bearing steels, improving micro-mechanical predictions.

Contribution

It introduces an integrated experimental and computational approach to quantify the micro-mechanical response of retained austenite in bearing steels.

Findings

Successfully predicted micro-mechanical and macro-mechanical responses.

Estimated elastic constants of austenite and martensite phases.

Validated the transformation behavior of retained austenite.

Abstract

This work integrates in-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in high carbon bearing steels. The presence of a kinematically metastable retained austenite in bearing steels can significantly affect the macro-mechanical and micro-mechanical material response. Mechanical characterization of metastable austenite is a critical component in accurately capturing the micro-mechanical behavior under typical application loads. Traditional mechanical characterization techniques are unable to discretely quantify the micro-mechanical response of the austenite, and as a result, the computational predictions rely heavily on trial and error or qualitative descriptions of the austenite phase. In order to overcome this, in this present work, we use in-situ neutron diffraction of a uniaxial tension test of an A485 Grade 1 bearing steel specimen. The mechanical response determined from the neutron diffraction analysis was incorporated into a hybrid crystal plasticity finite element model that accounts for the martensite's crystal plasticity and the stress-assisted transformation from austenite to martensite in bearing steels. The modeling response was used to estimate the single crystal elastic constants of the austenite and martensite phases. The results show that using in-situ neutron diffraction coupled with a crystal plasticity model, can successfully predict both the micro-mechanical and macro-mechanical responses of bearing steels while accounting for the martensitic transformation of the retained austenite.