Determination of the critical stress for the initiation of dynamic transformation in commercially pure titanium

Aranas, Clodualdo; Foul, Anes; Guo, Baoqi; Fall, Ameth; Jahazi, Mohammad; Jonas, John J.

doi:10.1016/j.scriptamat.2017.02.022

Cited by 30 publications

(6 citation statements)

References 11 publications

(15 reference statements)

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“…Therefore, the critical strain (and stress) using this method is always higher than the actual initiation point. This was also discussed by the present authors in a previous paper [14], however, this work was focused in the occurrence of dynamic transformation in pure titanium. The present work will provide an alternative approach to calculate the critical stress in steels by using the free energy difference between the phases and the yield stress of freshly formed ferrite at elevated temperature.…”

Section: Introductionsupporting

confidence: 65%

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

Aranas

Rodrigues

Fall

et al. 2018

Metals

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Abstract:The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT) because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method) is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region) and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 • C to 1070 • C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.

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Section: Introductionsupporting

confidence: 65%

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

Aranas

Rodrigues

Fall

et al. 2018

Metals

Self Cite

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“…It has been reported that the double differentiation technique overestimates the critical stress and strain since it requires the formation of about 5% of the dynamic phase in order for the operation of the softening mechanism to be detectable [37]. To overcome this barrier, the critical stresses are calculated by the total barrier energy method, which provides exact moment that transformation begins.…”

Section: Diffusion Analysis Of Alloying Elementsmentioning

confidence: 99%

On the Role of Chromium in Dynamic Transformation of Austenite

et al. 2018

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The effect of Chromium (Cr) on the dynamic transformation (DT) of austenite to ferrite at temperatures up to 430 °C above Ae3 was studied in a medium-carbon low-alloy steel.Hot compression tests were performed using Gleeble 3800 ® thermomechanical simulator followed by microstructural examinations using electron microscopy (FESEM-EBSD).Driving force calculation using austenite flow stress and ferrite yield stress on an inverse absolute temperature graph indicated that Cr increases the driving force for the transformation of austenite to ferrite; however, when the influence of stress and thermodynamic analysis are taken into account, it was observed that Cr increases the barrier energy and therefore, emerges as a barrier to the transformation. An analysis,

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“…Therefore, it is necessary to check the proportion of distortion energy in the free energy. The distortion energy [25]. If the reversal transformation occurs, the difference of ferrite flow stress and austenite yield stress will meet Eq.…”

Section: Reversal Austenizationmentioning

confidence: 99%

“…So, the influence of distortion energy on the transformation can be neglected, which is similar to the results reported in Refs. [25,29]. Therefore, the value of c is 265.93 MPa, based on Eqs.…”

Section: Reversal Austenizationmentioning

confidence: 99%

Ultra-fine-Grained Ferrite Prepared from Dynamic Reversal Austenite During Warm Deformation

Chen

Yaqiang

et al. 2019

Acta Metall. Sin. (Engl. Lett.)

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The ultra-fine-grained ferrite (UFGF) with the size of less than 1 μm is often difficult to be obtained for low-alloyed steel in practical production processing. In this study, considering the rod and wire production process, a new method for preparing the UFGF with submicron scale is proposed by warm deformation of six passes with total strain of 2.6, followed by the cooling process in Gleeble-3500 thermo-mechanical simulator. The results show that the UFGF with an average size of 0.64 μm could be obtained via the phase transformation from austenite grains with an average size of 3.4 μm, which are achieved by the deformation-induced reversal austenization during the high strain rate warm deformation. The main driving force for the reversal transformation is the stress. And the interval between the passes also plays an important role in the reversal austenization.

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Determination of the critical stress for the initiation of dynamic transformation in commercially pure titanium

Cited by 30 publications

References 11 publications

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

On the Role of Chromium in Dynamic Transformation of Austenite

Ultra-fine-Grained Ferrite Prepared from Dynamic Reversal Austenite During Warm Deformation

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