Journal of Materials Processing Technology 182 (2007) 207–214 Properties and deformation behaviour of severe plastic deformed aluminium alloys P. Leo a,∗ , E. Cerri a , P.P. De Marco a , H.J. Roven b a Department of Ingegneria dell’Innovazione, University of Lecce, via Arnesano, 73100 Lecce, Italy b NTNU, Department of Materials Science and Engineering, Alfred Getz vei 2, N-7491 Trondheim, Norway Received 28 July 2005; received in revised form 12 July 2006; accepted 27 July 2006 Abstract Two and three dimensional FEM analysis of different aluminium alloys by equal channel angular pressing using Abaqus code show lower equivalent plastic strain on outer side of both transverse and longitudinal sections of workpiece. HV hardness and microhardness tests on different ecapped alloys show that the outer sides of processed alloys also are characterized by lower values. Microstructure analysis of different areas of processed specimens after one pass indicate that the areas of lowest equivalent plastic strain exhibit an almost undeformed microstructure. Moreover the effect of strain hardening rate (SHR) has been investigated. According to FEM analysis a higher strain hardening rate leads to a larger natural corner gap, a lower equivalent plastic strain and a wider extension of outer less deformed zone. © 2006 Elsevier B.V. All rights reserved. Keywords: ECAP; FEM analysis; Strain hardening rate 1. Introduction Equal channel angular pressing (ECAP) is a very interest- ing method for modifying microstructure in producing ultra fine grained (UFG) materials. It consists of pressing test samples through a die containing two channels, equal in cross-section and intersecting at an angle Φ (Fig. 1). As a result of the press- ing, the sample deforms by simple shear [1,2] and retains the same cross-sectional area so that it is possible to repeat the press- ing for several cycles. The equivalent strain ε generated in the workpiece after one pass of ECAP is given by the following relation [3]: ε =  1 √ 3  2 cot  Φ 2 + Ψ 2  + Ψ cosec  Φ 2 + Ψ 2  (1) in which Ψ is the outer corner angle of ECAP die (Fig. 1). According to Eq. (1) the equivalent strain depends on both Φ and Ψ angles. It decreases if Ψ increases and its greatest value ( ∼ 1) is obtained if Φ = 90 ◦ and Ψ is close to zero [4]. UFG materials are characterized by higher strength, accord- ing to the Hall Petch relationship, and a higher toughness at ∗ Corresponding author. Tel.: +39 0832 297283; fax: +39 0832 325004. E-mail address: paola.leo@unile.it (P. Leo). ambient temperature. If the UFG microstructure is retained to elevated temperature too, there is also a potential for achieving superplastic formability [5]. To improve the quality of processed material it is essential to understand the deformation behaviour in the workpiece and the effect of materials properties on it [6]. In fact the microstructure and mechanical properties of the deformed materials are directly related to the degree of plastic deformation and to its homogeneity [7]. The plastic deformation behaviour is controlled by both die design parameters [2,8] and parameters related to material properties, strain rate sensitivity and hardening exponent [9]. In this paper three different 6082 alloys, two of them modi- fied with Zr and Sc–Zr, have been studied by microstructural and deformation behaviour points of view. It is well known that alloys of 6000 series are widely used in automotive and aerospace industries as a result of their good physical and chemical properties such as corrosion resistance, formability, weldability [10] and because they are age hardenable to develop adequate strength [11]. Moreover Sc and Zr additions play a critical role in these alloys by providing particles which impede grain growth at elevated temperatures to enhance superplasticity [12–19]. Finite element analysis (FEM) results have been related to microstructure and mechanical properties of ECAPed alloys. Moreover the effect of strain hardening rate (SHR) on mechan- 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.07.038