Microstructure evolution and mechanical properties of an AZ61 alloy processed with TS-ECAP and EPT

Abstract

The microstructure evolution and mechanical properties of an AZ61 alloy that was processed with a combination of two-step equal-channel angular pressing (TS-ECAP) and electropulsing treatment (EPT) processing were investigated herein. After the second-step ECAP (SS-ECAP) for 4 passes, the dislocation densities and stored deformation energy of the AZ61 alloy continuously accumulated to reach maximum values of 3.03 × 1014 m−2 and 41.2 J/g, respectively. The results were attributed to a decrease in the extrusion temperature, accumulated deformation and grain refinement. Compared with the properties of the as-received AZ61 alloy, the best comprehensive mechanical properties were obtained by the TS-ECAP and EPT method. First, the grain size of the samples after the EPT was refined from 30 μm to 1 μm. Second, the yield strength and tensile strength significantly increased from the initial values of 250 MPa and 350 MPa–305 MPa and 426 MPa, respectively. Additionally, the elongation was greatly improved from 6.8% to 18.3%, which is an increase of three times over that of the as-received AZ61 alloy. In conclusion, a uniform and ultrafine-grained structure was obtained in the samples after an EPT, where static recrystallization was completed at a relatively low temperatures and in a short time.