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Metastable austenite driven work-hardening behaviour in a TRIP-assisted dual phase steel

DOI: 10.1016/j.ijplas.2016.10.005 DOI Help

Authors: Bernard Ennis (Tata Steel (Netherlands)) , Enrique Jimenez-melero (University of Manchester) , E.h. Atzema (Tata Steel Research and Development) , M. Krugla (Tata Steel Research and Development) , Mohammed Azeem (University of Manchester) , Daniel Rowley (University of Manchester) , Dominik Daisenberger (Diamond Light Source) , D.n. Hanlon (Tata Steel Research and Development) , P. D. Lee (University of Manchester)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: International Journal Of Plasticity , VOL 88 , PAGES 126-139

State: Published (Approved)
Published: January 2017
Diamond Proposal Number(s): 4026

Open Access Open Access

Abstract: The mechanically-induced transformation behaviour of the metastable austenite phase in a high-strength industrial TRIP-assisted Dual Phase steel was monitored in situ using high-energy synchrotron diffraction under uniaxial loading. This allowed direct quantification of the impact of the transformation of the metastable austenite phase (16 vol %), embedded in a ferrite-bainite-martensite matrix, on the work hardening behaviour of this steel. Our results show that the mechanically induced transformation of austenite does not begin until the onset of matrix yielding. We provide experimental evidence which demonstrates for the first time that the austenite transformation increases the work-hardening contribution, σw thereby supporting a driving force approach to transformation induced plasticity. The transformation work required leads to an increase in the macroscopic work-hardening rate after matrix yielding and continues to offset the decrease in the work-hardening rate in the ferrite and martensite phases up to the UTS. Further we show conclusively that martensite yielding does not occur until the completion of the mechanically induced transformation of austenite. Plastic deformation of martensite is immediately followed by local plastic instability leading to necking and ultimate failure of this material.

Journal Keywords: Phase transformation; Crystal plasticity; Metallic materials; Mechanical testing; Synchrotron X-ray diffraction

Subject Areas: Materials, Engineering
Collaborations: Diamond Manchester

Instruments: I15-Extreme Conditions