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An In-Situ Synchrotron Diffraction Study of Stress Relaxation in Titanium: Effect of Temperature and Oxygen on Cold Dwell Fatigue

40 Pages Posted: 31 Dec 2020 Publication Status: Published

See all articles by Yi Xiong

Yi Xiong

University of Oxford - Department of Materials

Phani S. Karamched

University of Oxford - Department of Materials

Chi-Toan Nguyen

Safran Tech - Department of Materials and Process

David M. Collins

University of Birmingham - School of Metallurgy and Materials

Nicolò Grilli

University of Oxford - Department of Materials

Christopher M. Magazzeni

University of Oxford

Edmund Tarleton

University of Oxford - Department of Materials

Angus J. Wilkinson

University of Oxford - Department of Materials

Abstract

There is a long-standing technological problem in which a stress dwell during cyclic loading at room temperature in Ti causes a drastic fatigue life reduction. To better understand the material characteristics that control or exacerbate this behaviour, evaluation of the time dependent plasticity of the main prismatic and basal slip systems is critical. Incorporating the influence of operating temperatures and common alloying elements on cold dwell fatigue will be beneficial for future alloy design to address this problem. In this work, characterisation of the time dependent plastic behaviour of two commercially pure titanium samples (grade 1 and grade 4) with different oxygen content at 4 different temperatures (room temperature, 75 ºC, 145 ºC and 250 ºC) was performed during stress relaxation using synchrotron X-ray diffraction. Key parameters that govern the dislocation motion were determined for the major prismatic and basal slip systems as a function of temperature and oxygen content by calibrating a crystal plasticity finite element model with the measured lattice strain relaxation responses. From the temperatures assessed, 75 ºC is found to be the worse-case scenario, where the macroscopic plastic strain accumulation was the significant during a relaxation cycle due to the greatest activity of both prism and basal slip systems. As temperature increases, the contribution of thermal energy becomes greater than mechanical energy for dislocation glide. Oxygen was found to have a stronger strengthening effect on prism slip over basal slip, through a significant change in their respective critical resolved shear stresses. This effect becomes more significant in higher oxygen content commercially pure Ti.

Suggested Citation

Xiong, Yi and Karamched, Phani S. and Nguyen, Chi-Toan and Collins, David M. and Grilli, Nicolò and Magazzeni, Christopher M. and Tarleton, Edmund and Wilkinson, Angus J., An In-Situ Synchrotron Diffraction Study of Stress Relaxation in Titanium: Effect of Temperature and Oxygen on Cold Dwell Fatigue. Available at SSRN: https://ssrn.com/abstract=3757762 or http://dx.doi.org/10.2139/ssrn.3757762

Yi Xiong (Contact Author)

University of Oxford - Department of Materials ( email )

Parks Road
Oxford, OX1 3PH
United Kingdom

Phani S. Karamched

University of Oxford - Department of Materials ( email )

Chi-Toan Nguyen

Safran Tech - Department of Materials and Process

Châteaufort, 78772
France

David M. Collins

University of Birmingham - School of Metallurgy and Materials ( email )

Edgbaston, Birmingham B15 2TT
United Kingdom

Nicolò Grilli

University of Oxford - Department of Materials ( email )

Mansfield Road
Oxford, OX1 4AU
United Kingdom

Christopher M. Magazzeni

University of Oxford

Mansfield Road
Oxford, OX1 4AU
United Kingdom

Edmund Tarleton

University of Oxford - Department of Materials

Parks Road
Oxford, OX1 3PH
United Kingdom

Angus J. Wilkinson

University of Oxford - Department of Materials

Parks Road
Oxford, OX1 3PH
United Kingdom

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