The effects of room temperature ECAP and subsequent aging on mechanical properties of 2024 Al alloy M.H. Goodarzy a,⇑ , H. Arabi b , M.A. Boutorabi b , S.H. Seyedein a , S.H. Hasani Najafabadi c a School of Metallurgy and Materials Engineering, Iran University of Science & Technology (IUST), Narmak, Tehran 13114-16846, Iran b Center of Excellence for High Strength Alloys Technology (CEHSAT), School of Metallurgy and Materials Engineering (IUST), Narmak, Tehran 13114-16846, Iran c Department of Mechanical Engineering, Azad University Saveh Branch (AUSB), Saveh 39187-366, Iran article info Article history: Received 9 April 2013 Received in revised form 27 September 2013 Accepted 30 September 2013 Available online 14 October 2013 Keywords: ECAP 2024 Aluminum alloy Aging Mechanical properties abstract Mechanical properties of the 2024 aluminum alloy, which was plastically deformed by equal channel angular pressing (ECAP) at room temperature and aged naturally and artificially at 70 °C and 100 °C for different times, were investigated in this research. Many of the short shear bands were observed on the microstructure after one pass of ECAP and led to fragmentation of grains. Hardness and yield stress of the sample aged naturally after deformation were considerably improved due to increase of dislocation density calculated by XRD data analysis and their interaction with solute atoms during ECAP. The ductil- ity and work hardening exponent of the deformed samples were significantly reduced due to formation of shear bands within the microstructure. However aging the samples immediately after sever plastic defor- mation at 70 °C and 100 °C caused an additional improvement in hardness and yield stress relative to the samples aged naturally after deformation. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Mechanical properties of metal alloys can be improved by form- ing processes such as ECAP [1,2]. This process presented by Segal et al. [3] at 1977 has been widely used by many researchers since then [4,5]. Mechanical properties of most age-hardenable alumi- num alloys can be improved by this method. It is well known that the most part of improvement in mechanical properties of the fully annealed aluminum alloys is achieved in the first pass of ECAP pro- cess [4,6]. For example according to Horita et al. [6] fully annealed Al alloys such as 1100, 6061 and 7075 can obtain 80–90% of their maximum values of their yield stress only after one pass ECAP. Also some reports indicate that a significant improvement in mechani- cal properties of age hardenable aluminum alloys in solution annealing condition, can be achieved via one pass of warm ECAP and subsequent aging at low temperatures [6–8]. For example according to Kim et al. [8], the yield stress of 2024 aluminum alloy can be improved by 110%, i.e. from 320 MPa to 628 MPa after one pass of warm ECAP and subsequent aging at 100 °C for 20–30 h. It has been reported [8,9] that increase in the dislocation density during ECAP not only improves material strengthening, but also it can increase the rate of precipitation during aging. So that forma- tion of fine precipitates and further improvement in mechanical properties can be expected. However, dynamic recovery in warm ECAP of age hardenable Al alloys can cause a decrease in dislocation density of the deformed material and consequently dislocation strengthening is decreased [10,11]; one should consider cold ECAP as a substitute for deformation of these material. Recently some published reports show that improvement in mechanical proper- ties can be achieved by one pass of cold ECAP in age hardenable alu- minum alloy [12–14] due to elimination of dynamic recovery in this process which cause saturation in subgrain dislocation density, hence optimum mechanical properties are achieved [15]. Moreover from economic point of view, according to Bidulsky [16], using one pass of cold ECAP is beneficial for making aluminum PM parts, as application of this process can control the porosity content. Deformation of aluminum alloys EN AW 2014 by one pass of cold ECAP after solution annealing and water quenching, resulted to improvement of its yield stress from 157 MPa to 511 MPa due to grain refinement and strain hardening of solid solution accord- ing to Kvackaj et al. [12,13]. However, subsequent artificial aging at 100 °C did not considerably affect YS & UTS of the ECAPed alloy. In another study, Danaf [14] reported that the usage of one pass of cold ECAP for commercial Al alloys 1050, 5083, 6082 and 7010 re- sult to domination of low angle grain boundaries within the micro- structure of ECAPed alloys. The amount of decrease in grain size in his study was considerable especially in age hardenable alloys 6082 and 7010. In addition hardness and yield strength of the ECAPed alloys were sharply increased due to grain refinement and dislocation strengthening during cold ECAP. The above mentioned reports basically related to the cold ECAP of some Al alloys at room temperature, does not include 2024 Al 0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.09.202 ⇑ Corresponding author. Tel./fax: +98 2177459151. E-mail addresses: mh_goodarzy@iust.ac.ir (M.H. Goodarzy), arabi@iust.ac.ir (H. Arabi), boutorabi@iust.ac.ir (M.A. Boutorabi), seyedein@iust.ac.ir (S.H. Seyedein), najafabadiresearch@gmail.com (S.H. Hasani Najafabadi). Journal of Alloys and Compounds 585 (2014) 753–759 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom