EFFECTS OF ROTARY-DIE ECAP ROUTES ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF AZ31 MAGNESIUM ALLOY

Using a 3D rotary-die equal-channel angular pressing (3D-RD ECAP) mold, the commercial wrought magnesium alloy AZ31 has been processed through 4 routes(A', BA', BC' and C') and microstructures as well as mechanical properties of the samples processed were investigated. The results reveal that all the 4 routes can refine microstructures of the alloy, however, the effects on microstructural homogeneity and tensile elongations of the samples are different. The grain sizes of the samples processed through routes A' or BA' are more uniform and their tensile elongations at ambient temperature are also higher than those through BC' or C' routes. The distributions of hardness on the central longitudinal planes of samples extruded through different routes are well consistent with the microstructural characters at the corresponding positions. Strain analysis on the cubic elements in the samples reveals the limitation of the traditional shear mode for ECAP. Based on experimental results and finite element method (FEM) simulation, the deformation homogeneity caused by ECAP processing is closely related to the alternative action of tensile and compressive stresses at the different positions in the samples and is independent of the deformation regularity of the cubic elements in the shear model proposed in the previous studies.