Microstructural and Mechanical Properties of a Material Processed by Streamline Proposed Vortex Extrusion Die
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Microstructural and Mechanical Properties of a Material Processed by Streamline Proposed Vortex Extrusion Die M. Shahbaz1 · N. Pardis2 · J. Moon3 · R. Ebrahimi2 · H. S. Kim3 Received: 6 June 2020 / Accepted: 6 August 2020 © The Korean Institute of Metals and Materials 2020
Abstract Vortex extrusion (VE), as a severe plastic deformation technique, uses a novel designed stationary die that imposes intense strain to the processed material. Materials in the VE process experience torsional deformation and simultaneous reduction in area. The amount and intensity of this additional deformation vary according to the radius moving from the center to the surface of the VE die due to variations in the path of the material through a radius proposed by the Beziers’ formulation. In the present study, the VE die is designed through a streamline approach based on a cubic Beziers’ formulation that was employed to investigate the microstructural and mechanical properties of the processed samples and to link the results to those obtained through a finite element analysis of this technique. The results of the microstructural characterization exhibit a higher fraction of high-angle grain boundaries of the VE processed samples compared to what can be achieved by conventional extrusion-processed. Consequently, a significant improvement was observed in tensile properties of the samples after SPD processing using the proposed streamlined VE die. Keywords Severe plastic deformation · Vortex extrusion · Streamline approach · Microstructure · Mechanical properties
1 Introduction Metallic materials can be processed by severe plastic deformation (SPD) as a top-down approach that results in extreme grain refinement at the sub-micrometer and sometimes nanometer scales for improving mechanical properties of the processed materials [1, 2]. A high level of plastic strain can be imposed through batch SPD processes such as, equal channel angular pressing/extrusion (ECAP/ECAE) [3], single-roll angular-rolling (SRAR) [4], cyclic expansionextrusion (CEE) [5–7], twist extrusion (TE) [8, 9], hollow twist extrusion [10] and off-axis twist extrusion [11], or single-pass ones like torsion extrusion [12], vortex extrusion [13–18], rotating backward extrusion (RBE) [19] and * M. Shahbaz [email protected] 1
Department of Materials Science and Engineering, Faculty of Engineering, Urmia University, Urmia 15311‑57561, Iran
2
Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz 71946‑84334, Iran
3
Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
rectangular vortex extrusion (RVE) [20]. Single-pass SPD processes, however, increase productivity by reducing the required processing steps. Considering the key role of the accumulated strain in the first pass of batch SPD techniques on the final microstructure of processed samples [3], singlepass techniques benefit the high strain value accumulated via single-pass process
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