Hydrostatic cyclic extrusion compression (HCEC) process; a new CEC counterpart for processing long ultrafine-grained met
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(2020) 20:108
ORIGINAL ARTICLE
Hydrostatic cyclic extrusion compression (HCEC) process; a new CEC counterpart for processing long ultrafine‑grained metals Armin Siahsarani1 · Ghader Faraji1 Received: 19 May 2020 / Revised: 18 August 2020 / Accepted: 31 August 2020 © Wroclaw University of Science and Technology 2020
Abstract Hydrostatic cyclic extrusion–compression as a novel severe plastic deformation method in the processing of the rods is introduced and used for refining ultrafine-grained commercial pure aluminum. HCEC is solving the limitation of the conventional CEC in producing long-length samples by utilizing pressurized hydraulic fluid and eliminating the frictional effects. An increase in the length of the processable sample, a reduction in the processing loads, an intensification in the hydrostatic stress, and improvement in the strain distribution are the novel achievements of the HCEC. The capability of HCEC in grain refinement of the commercial pure aluminum was investigated by transmission electron microscopy analysis. The processed samples showed the grain sizes of 780 nm and 400 nm after the first and second passes of the HCEC, respectively. Furthermore, tensile and shear punch tests were utilized for investigation of the mechanical properties of the unprocessed and HCEC processed rods. An increase in the tensile and shear yield and ultimate strengths after the process confirmed the decreases in grain sizes. The tensile yield and ultimate strengths of the rod after the second cycle of the process reached 170 and 196 MPa, respectively. The same increasing trend as strength was shown in the microhardness after the HCEC. FEM analysis depicted the homogenous distribution of strain along the length of the sample. Also, the independency of the processing force to the length of the sample was shown by the FEM. The implementation of this novel technique looks very interesting for the industrial utilization of SPD techniques, especially in automotive and aerospace industries, which suffer from the limited size of the processing specimens. Keywords Severe plastic deformation · Hydrostatic cyclic extrusion-compression · Pressurized fluid · Transmission electron microscopy · Tensile test · Shear punch test · Microhardness
1 Introduction The increasing demand for the lightweight and simultaneously high strength metals has attracted the attention of many industries and researchers to the employment of severe plastic deformation (SPD) techniques, and especially the methods advanced for the development of ultrafine-grained (UFG) and nano-grained (NG) metals [1]. By implementation of the SPD techniques, higher strains that exceed the values of the conventional forming methods like extrusion is applied to the material; This higher values of strain refines the microstructure of the material to the nanometric dimensions [2]. Among various SPD processes, extrusion-based * Ghader Faraji [email protected] 1
School of Mechanical Engineering, College of Engineering, University of Tehran, 11155‑4563 Tehran, Iran
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