Effect of Temperature on Strength and Hardness in Multi-pass Equal Channel Angular Pressing (ECAP) of Aluminum Alloys

Abstract

In the Equal channel angular pressing (ECAP) process, the sample passes through the channel and the shear stress applied to the sample leads to grain refinement and consequently, the mechanical properties of the sample will be increased. In this article, the effect of implementing the ECAP process at elevated temperature on the strength and hardness of the samples will be studied. Commercially pure (99.0% Al) and AA6063 aluminum round bars are prepared and ECAPed in a die with channel angle of $$\phi$$ = 120° and a corner angle of $$\varphi$$ = 20°. The tensile strength and hardness are compared for 1–8 pass ECAPed samples at 150 °C and room temperature. Also, the ECAP process is modeled in a finite element software to predict the plastic strain distribution in repetitive passes of ECAP. The results show that performing ECAP at elevated temperature decreases the tensile strength by about 5% and 12% in the AA6063 and commercially pure aluminum alloy samples, respectively. Also, at 150 °C, the percent of the increase in the tensile strength decreases in pass #1 but at pass #8 of ECAP, the percent of increase in the tensile strength is equal. So, decrease in the tensile strength in initial passes cannot be compensated by repetition of the ECAP process and at higher passes the strain saturation does not allow to recompense the decrease in the strength at initial passes. The finite element results show that the plastic strain heterogeneity and the value of equivalent plastic strain obtained from FEM are comparable with analytical formulations proposed by other researchers with acceptable error.