Investigation of Microstructure, Mechanical Properties and Residual Stress in Non-equal-Channel Angular Pressing of 6061 Aluminum Alloy

Abstract

In equal-channel angular pressing, it is necessary to repeat the process to achieve large strains. However, in non-equal-channel angular pressing (NECAP), the large strains can be achieved without repetition of the process. In this study, the effect of the NECAP on microstructure, mechanical properties and residual stress (RS) of widely used 6061 aluminum alloy sample was investigated. After the NECAP process, yield strength, tensile strength, hardness and uniformity of the hardness distribution increased dramatically and fracture strain and tensile toughness were significantly reduced. The effect of the NECAP on the yield strength was significantly higher than other parameters of the mechanical properties. Also, the microstructure was obtained with more uniformity and with the grain size of 18.5 times smaller relative to the initial sample. The numerical simulation results showed that by increasing friction coefficient, the plastic strain increases. In this study, a very good agreement was obtained between the results of experimental method of contour and finite element method in the RS measuring. In this paper, the RS factor (R.S.F.) was introduced to investigate the RS distribution. With the aid of this factor, one can obtain a general understanding of the RS distribution in one part. In this research, the effect of the friction coefficient on the R.S.F. in surfaces and middle cross section of the NECAPed sample was discussed.