Severe plastic deformation of tubular AA 6061 via equal channel angular pressing

Abstract

Various severe plastic deformation (SPD) processes have been developed to produce metal tubes with ultrafine grain (UFG) structures. However, most techniques are complex and limited to working with components that are short in length to avoid tube failure during SPD processes. To overcome such limitations, this study suggests the use of an equal channel angular pressing (ECAP) process for the production of tubular aluminum alloy 6061. To mitigate plastic instability effects such as tube buckling and fracture during processing, hydraulic oil was used to fill the tube cavity. Finite element analysis (FEA) using Abaqus/Explicit 6.13 was carried out to examine the feasibility of the proposed method and deformation mechanism during ECAP. A series of investigations were performed, including: microstructure analysis, torsion, and micro hardness tests to evaluate the effects of tube-ECAP treatment. Test results indicated that the resultant 60% reduction in grain size led to significant mechanical property improvements including yield shear strength, ultimate shear strength, and microhardness. However, the ductility of the material decreased slightly for the ECAP-treated samples. To resolve this issue, a heat treatment process using the T6 method was performed, leading to a notable ductility enhancement in addition to further improvements in shear strength and microhardness. (c) 2015 Elsevier Ltd. All rights reserved.