Materials Science & Engineering A 776 (2020) 139002 Available online 30 January 2020 0921-5093/© 2020 Elsevier B.V. All rights reserved. Comparison of the effects of isothermal equal channel angular pressing and multi-directional forging on mechanical properties of AM60 magnesium alloy M.A. Salevati a , F. Akbaripanah a, * , R. Mahmudi b , K.H. Fekete c, d , A. Heczel e , J. Gubicza e a Department of Mechanical Engineering, Faculty of Engineering, Malayer University, Malayer, Iran b School of Metallurgical and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran c Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic d Nuclear Physics Institute of the CAS, Rez, Czech Republic e Department of Materials Physics, E€ otv€ os Lor� and University Budapest, P.O.B. 32, H-1518, Hungary A R T I C L E INFO Keywords: AM60 alloy Equal channel angular pressing Multi-directional forging Microstructure Mechanical properties ABSTRACT This study investigates the correlation between the microstructure and the mechanical strength of AM60 mag- nesium alloy processed by equal channel angular pressing (ECAP) and multi-directional forging (MDF) at a constant temperature of 220 � C. The maximum number of passes was six for both severe plastic deformation (SPD) techniques. The minimum achievable grain size was ~1.9 μm for ECAP while it was only ~2.7 μm for MDF. Despite the monotonous reduction of the grain size, the yield and the ultimate tensile strength values decreased for high equivalent strains which was attributed to the decrease of the dislocation density. The maximum achievable strength was higher for ECAP than that for MDF mainly due to the higher dislocation density. Both ECAP and MDF processing led to an improvement of ductility. Based on the strength results, it is evident that the ECAP process is more effective in improving the mechanical properties of AM60 alloy at 220 � C, compared to the MDF process. 1. Introduction In recent years, ultrafne-grained (UFG) materials processed by se- vere plastic deformation (SPD) are in the focus of materials science. These materials exhibit high mechanical strength, therefore, they have a high potential for using as structural components in various practical applications [1]. The most frequently used SPD methods are equal channel angular pressing (ECAP), multi-directional forging (MDF), accumulated roll bonding (ARB) and high-pressure torsion (HPT) [2]. In these processes, the material is subjected to severe strains in several steps, leading to the reduction of the grain size to submicron or even nano-metric levels [3]. Since dimensional changes during the processing of materials may hinder their broad practical applications, the majority of SPD methods are designed in such a way that the sample dimensions remain practically unchanged during the process. UFG materials pro- cessed by SPD usually have equiaxed grains and a large fraction of high angle grain boundaries [4]. The presence of large quantities of high angle grain boundaries makes it easier to achieve the desired properties [5]. SPD of magnesium (Mg) alloys is often carried out at temperatures higher than 200 � C due to their low room-temperature ductility [6]. ECAP is the frst SPD method which was introduced in 1981 [7,8]. The sample is mainly deformed by shear when crossing the junction of the two ECAP channels. Since the dimensions of the sample remain constant, it is possible to reuse the same sample to create severe strains. By rotating the sample in subsequent passes, it is also possible to apply different shear forces [9]. The fnal grain size obtained by ECAP depends on the deformation temperature, the route, the number of passes, the angle between the two channels (ψ), the angle describing the outer arc of curvature (ϕ) and the strain rate. The most homogenous structures are produced using route B C [10,11]. Former studies have shown that ECAP processing through route B C can lead to an enhancement of homogeneity of grain structure and a reduction of grain size [12–14], an increased surface hardness [6,12] and improvement of tensile and shear properties [6,12,14]. The microstructural refnement, obtained by SPD, has been found to be benefcial for increasing both ductility and strength of Mg alloys. * Corresponding author. E-mail address: f.akbaripanah@malayeru.ac.ir (F. Akbaripanah). Contents lists available at ScienceDirect Materials Science & Engineering A journal homepage: http://www.elsevier.com/locate/msea https://doi.org/10.1016/j.msea.2020.139002 Received 4 September 2019; Received in revised form 22 January 2020; Accepted 23 January 2020