Application of T-shape friction test for AZ31 and AZ80 magnesium alloys at elevated temperatures F. Fereshteh-Saniee ⇑ , H. Badnava, S.M. Pezeshki-Najafabadi Department of Mechanical Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan 65178, Iran article info Article history: Received 6 October 2010 Accepted 17 February 2011 Available online 20 February 2011 Keywords: A. Non-ferrous metals and alloys C. Forming E. Mechanical abstract T-shape side pressing experiment is a sort of friction test which, recently, is employed for evaluation of friction for bulk metal forming processes. One of important advantages of this experiment, compared with other friction tests such as the ring compression test, is the occurrence of appropriate surface enlargement during the deformation of the specimen. This paper is concerned with experimental and numerical studies on this test, when it is used for some magnesium alloys such as AZ31 and AZ80. Based on the experimental results, it was found that the friction sensitivity of T-shape experiment increased when the die edge radius decreased or the test temperature or ram velocity increased. Good repeatability of this test was also observed during experimental part of this research work. Finally, employing the ﬂow curves gained from the compression tests and friction factors obtained from the T-shape experiments for the ﬁnite-element simulations of this test, resulted in a very good agreement between the numerical and experimental load curves. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Magnesium alloys are extensively used in various industries such as automotive, aerospace and electronic industries. This is in- debted to some important characteristics of these alloys such as high strength/weight ratio, good wear resistance, recyclability and high weldability and thermal conductivity [1,2]. To improve the strength and soundness of magnesium alloys, after the casting process, they are subjected to one of forming operation, such as forging, extrusion or rolling [3]. However, because of hexagonal closed pack (hcp) structure of magnesium alloys, they represent poor formability and very limited ductility at the room tempera- ture [4,5]. That is why a magnesium alloy is usually deformed un- der warm or hot conditions. An important parameter affecting the deformation of magnesium alloys at elevated temperatures is the friction. The forming load, the die wear and surface ﬁnish of the product are signiﬁcantly inﬂuenced by the friction. For this reason, an appropriate evaluation of this parameter is very essen- tial in metal forming, especially for high temperatures. There are several friction tests, each having its advantages and shortcomings. Among them, the famous ones employed in bulk metal forming are the ring test, double-cup extrusion test, forward rod-backward cup extrusion test and the spike test [6]. A suitable friction experiment should provide conditions as similar as possi- ble to those usually observable in most the practical forming operations. These conditions are often related to the interfacial pressure and the surface enlargement. Recently, a relatively new friction experiment, namely T-shape side pressing test has been proposed [7]. T-shape side pressing test is quite a new friction test. Therefore, it is necessary to investigate the effect of various parameters on this experiment. This paper is concerned with numerical and experimental studies on T-shape friction test at elevated tempera- tures. The practical tests were conducted at various temperatures, ram velocities and friction conditions on the specimens made of AZ31 and AZ80 magnesium alloys. The inﬂuence of the die edge ra- dius was also investigated experimentally in this research work. The frictional conditions involved the dry condition and using MoS2 and a copper anti seize paste (CASP) as the lubricants. By using the friction factors obtained from the friction tests and the ﬂow curves gained from the practical compression tests, ﬁnite- element (FE) simulations of T-shape experiments were conducted and an encouragingly good agreement was found between the experimental and numerical load-displacement curves. 2. Friction tests and models The ring test is almost the simplest friction experiment, which have been experimentally used in various investigations [6,8]. In this experiment, a ring sample with speciﬁed initial outer diameter (OD)/inner diameter (ID)/height (H o ) ratio is pressed between two ﬂat platens. The internal diameter of the deformed ring may decrease (for low frictions) or increase (for high frictions). 0261-3069/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2011.02.042 ⇑ Corresponding author. Tel.: +98 811 8257406; fax: +98 8118257400. E-mail address: ffsaniee@basu.ac.ir (F. Fereshteh-Saniee). Materials and Design 32 (2011) 3221–3230 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes