Effects of high straining in copper strips processed by multiple direct extrusion and subsequent rolling

• Published in: IOP conference series. Materials Science and Engineering 2018-08, Vol.400 (3), p.32005
• Main Authors: Comaneci, R, Bujoreanu, L-G, Popa, M
• Format: Article
• Language: English
• Subjects: Copper; Elongation; Extrusion dies; Grain refinement; Mechanical properties; Plastic deformation; Room temperature; Tensile strength; Tensile tests; Workpieces
• ISSN: 1757-8981; 1757-899X; 1757-899X
• DOI: 10.1088/1757-899X/400/3/032005

As a novel severe plastic deformation (SPD) method, multiple direct extrusion (MDE) has been proposed as a new technique based on conventional deformation, consisting in repetitive extrusion processes of initial-squared cross-sectional workpieces, followed by transversal cutting, overlapping the resulting halves and resuming the extrusion by reinserting samples in the same die. Four cycles of MDE (route B) were applied to commercial copper and the potential for grain refinement and improvement in mechanical properties were evaluated. Because after the 3rd pass MDE(route A) a buckling instability was noticed, a series of comparative experiments by simple and combined rolling (R) and MDE, respectively, were undertaken. Tensile testing conducted at room temperature using a computer-controlled testing machine was carried out to evaluate the mechanical properties after each MDE and/or R cycle. Tensile strength and elongation at fracture after MDE, R and MDE + R, respectively, were analysed. It was found that after MDE cycle (route B), tensile strength is more than two times higher than that of the initial state and the elongation at fracture decreases not less than 25%. Combining MDE and R does not give a new increasing in strength that remains almost the same but decreases elongation at fracture.