Compression tests were made on a medium carbon vanadium steel to simulate the open die forging process of a 40-tons ingot. Several temperatures were used to consider the temperature gradient and the subsequent microstructural evolution. Indeed, multiple microstructural phenomena happened during forging step. Stress strain curves were generated from compression tests. We consider here four strain rates available on a hydraulic press and the deformation level that represent open die forging conditions. Friction and adiabatic heating were considered and corrected. Kinetic of DRX was analyzed and a hyperbolic sine Arrhenius type equation is proposed. Application of the constitutive modeling allowed us to find the deformation energy that is about 374kJ.
For the industrial field, this study has for purpose to harvest datas on a deformed steel. These datas are used in finite element analysis method to predict the evolution of the deformed microstructure in a whole 40 tons ingot. The scientist goal is to quantify the interaction between precipitates and dynamic recrystallization. It is then possible to predict if the matrix has enough energy to initiate dynamic recrystallization.
Results demonstrated that the kinetic of dynamic recrystallization is accelerated with increasing temperatures as well as increasing strain rate. Above a certain strain rate, the kinetics of dynamic recrystallization is rendered difficult. Micrographies show that dynamic recrystallization occurs in the microstructure which presented a peak in its flow curve. Analysis with scanning electron microscope revealed the presence of precipitate. These precipitates are interacting with dynamic recrystallization according to the comparison between the Zener pinning force and the dynamic recrystallization forces.
| Date | 19 Jan 2022 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Mohammad Jahazi (Supervisor) |
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Khan, M. (Author),
Jahazi (Supervisor),
19 Jan 2022Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering