Enhanced microstructure homogeneity and mechanical properties of AZ31 magnesium alloy by repetitive upsetting

An as-cast AZ31 Mg alloy in the form of thick plate (100 mm diameter and 20 mm height) with an initial grain size ∼200 μm was processed by a novel severe plastic deformation technique, repetitive upsetting (RU). Experiments were carried out for 1, 3, and 5 deformation passes at 250, 300, and 350 °C through route A and route B. Finite element analysis of the deformation process indicates homogeneous deformation during RU. With the number of RU passes, a finer grain size and more uniform microstructure are obtained along with significant improvement in both strength and ductility. A homogeneous grain structure with an averaged grain size of ∼2.6 μm through route A and ∼1.6 μm through route B are achieved after 5 passes at 350 °C. A tensile strength of 304 MPa and elongation of 28% are obtained in route B RU processing. AZ31 alloy exhibits a mean grain size of 1.3 μm and yield strength of 294 MPa and tensile strength of 354 MPa after 5 RU passes at 250 °C as compared to initial 43 MPa and 174 MPa, respectively.