Materials Science and Engineering A 410–411 (2005) 234–238 Using the stress–strain relationships to propose regions of low and high temperature plastic deformation in aluminum Nguyen Q. Chinh a,∗ , Judit Illy a , Zenji Horita b , Terence G. Langdon c a Department of General Physics, E¨ otv¨ os University, 1117 Budapest, P´ azm´ any P. s´ et´ any 1/A., Hungary b Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 812-8581, Japan c Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453, USA Received in revised form 19 April 2005 Abstract The plastic deformation of pure aluminum was investigated by tensile testing over a wide range of temperatures. In the region of positive work- hardening, it is shown that the stress–strain relationship can be described by an exponential-power law constitutive equation that was proposed recently and, in addition, this equation leads to a definition of the low and high temperature deformation regions. In the low temperature region, the macroscopic stress–strain behavior increases monotonously over a wide range of strain whereas at high testing temperatures the flow stress increases only up to a critical strain level. For pure aluminum, it is shown that the boundary between these two regions occurs at an homologous temperature of the order of ∼0.51 T m where T m is the absolute melting temperature. It is demonstrated that some important characteristics of the high temperature deformation process may be determined through the application of this new constitutive relationship. © 2005 Elsevier B.V. All rights reserved. Keywords: Aluminum; Constitutive equation; Plastic deformation; Stress–strain relationship 1. Introduction It is well known that recovery processes, in terms of differ- ent dislocation mechanisms, control the behavior of crystalline materials undergoing plastic deformation. Furthermore, for any specific testing conditions of strain rate and grain size, these mechanisms depend critically upon the temperature so that the temperature of testing becomes the dominant factor in deter- mining the overall behavior [1–4]. In most studies to date, whether experimental or theoretical, the investigations have been restricted so that they cover relatively low strains at the lower temperatures of deformation and relatively high strains under creep conditions at the higher temperatures of deforma- tion. In the regime at the lower temperatures where deformation occurs through thermal activation, attention is generally directed primarily to the work-hardening behavior. By contrast, at the higher temperatures in the diffusion-controlled regime, attention is usually focused on the nature of the creep mechanisms occur- ∗ Corresponding author. Tel.: +36 1 372 2815; fax: +36 1 372 2811. E-mail address: chinh@metal.elte.hu (N.Q. Chinh). ring under steady-state conditions at large strains. Although the work-hardening of polycrystalline metals has been the subject of numerous detailed investigations over a period of many years, it has proven impossible to date to develop a reasonably complete understanding because of the difficulties of predicting the nature of the behavior at very large strains. In practice, several models have been proposed to describe the stress–strain (σ –ε) relation- ship at both low and high strains [5–10]. However, an alternative approach was developed recently for pure Al and pure Cu where it was shown that, in the temperature range between 293 and 473 K, the macroscopic σ –ε relationship may be described in a simple way through a new exponential-power law constitutive relationship which applies equally well over the entire range of strain [11]. The present paper extends this earlier approach by inves- tigating the stress–strain relationship of pure Al over a much wider range of temperatures. Continuing the earlier study [11], the low and high temperature regimes of plastic deformation will be described using the new constitutive relationship and, in addition, this paper will delineate some of the parameters which serve to characterize the plastic deformation of Al over wide ranges of strain and temperature. 0921-5093/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2005.08.086