FUTAJEET 9 (2) (2015) (66-70) Influence of Accumulative back Extrusion and Lubricants on the Hardness of Al 6063 Alloy Ajiboye J. S. and Okey-Amechi B. A. Department of Mechanical Engineering, University of Lagos, Nigeria A B S T R A C T Keywords: ABE; hardness properties, lubricant Correspondence: E-mail address: josyboye@gmail.com 1. Introduction Severe plastic deformation processes can be defined as those processes that induce very high plastic strain in a metal in order to cause grain refinement. The equal-channel angular extrusion/pressing (ECAE/P) process was developed in Russia during the 1970s (Segal 1977; Segal, et al. 1981) as a method for introducing large plastic strains in a metal, while maintaining the outer dimensions of the work piece substantially unchanged. Though such processes have been known for many decades, there has been a recent upsurge in a new class of SPD processes which generally have one characteristic feature, namely the size and shape of the work-piece remains unchanged after SPD processing. The new SPD processes, such as equal channel angular extrusion or pressing (ECAE/P), high pressure torsion (HPT), accumulative roll bonding (ARB) and multi-axial compression/forging (MAC/F) all aim to keep the starting and finishing work piece shapes the same. ECAE/P, is discussed below, followed by some of the other processes. Among the processes discussed some like ECAE/P, MAC/F, and HPT introduce severe plastic deformation on bulk materials, while others like ARB, RCS, and Con-shear work on sheet materials. In all these techniques, a very large amount of de-formation is achieved without any shape change. However, the large friction be-tween the workpiece and the tools is considered as the primary drawbacks of the ECAE/P process in which most material currently produced consist only of small cross- sections and short lengths for laboratory studies. Equally, there is a substantial amount of undeformed material at the leading and training end of each piece. Segal et al. (1995) and Semiatin et al. (1999) addressed the problem of the high frictional forces by developing a complex die in which the floor of the exit channel moved along with the work piece. Back extrusion is considered a useful industrial method to create better surface finish, good dimensional control and lower required force comparing to the conventional extrusion. Harnessing the outstanding capabilities of back extrusion methods, Fatemi-Varzaneh and Zarei-Hanzaki, (2009) proposed accumulative back extrusion (ABE) as a novel bulk deformation technique. A twin punch setup, designed to slide through each other, formed the heart of this novel technique. As a relatively new severe plastic deformation technique, twist extrusion requires in-depth investigation of its plastic deformation characteristics. In this study, the twist extrusion process with a square shape die cavity has been analyzed using an upper bound solution to estimate the required power, deformation pattern, and optimum process condition. The analysis has been performed based on two kinematically admissible velocity fields while the effects of friction condition, die geometry, and mean equivalent strain have been considered Seyed, et. al., 2014;Marat, et. Al., 2015; and ChengPeng, et. Al 2012. A further defining feature of SPD techniques is that the preservation of shape is achieved due to special tool geometries which prevent the free flow of material and thereby produce a significant hydrostatic pressure. The presence of a high hydrostatic pressure, in combination with large shear strains, is essential for producing high densities of crystal lattice defects, particularly dislocations, which results in a significant The current accumulative back extrusion (ABE), a severe plastic deformation (SPD) process, is intends to improve hardness of commercially available Al 6063 alloy without compromising its ductility after undergoing plastic deformation. The novel technique consists of three innovative punch setup design to act sequentially. The first punch, smaller than the billet, pierce through with excess material flowing backward forming a cup shape, this is followed by the second punch, which is hollow, pushing the cup flanged back and thereby pushing the inner punch backward, extruding a rod. The final stage of pushing the whole billet back to the initial size and shape is achieved by the third punch which has the same diameter as the billet. This technique (ABE) was applied to a commercially aluminum specimen AA6063 to see the possible degree of improvement. It was discovered that the hardness of AA6063 was increased from 15HRE to 26HRE during cup extrusion and to 37HRE after the final stage of rod extrusion in a single operation. The whole cycle can be repeated to achieve higher hardness and improve mechanical properties. 66