The effect of dual thermomechanical processing paths on resulting microstructure and quasi-static mechanical properties of Mg-1Zn-0.2Ca

Abstract

In this work, cast Mg-1Zn-0.2Ca (wt%) was thermomechanically processed using a two-step procedure to identify the impact of both processing steps on the resulting microstructure and mechanical properties. Samples were first preprocessed via rolling or conventional extrusion (at 400 °C), followed by Equal Channel Angular Extrusion (ECAE), utilizing routes A or Bc. ECAE was performed at 300 °C for the first pass, followed by 275 °C, 250 °C, and 225 °C for passes 2–4. Subsequent microstructures, textures, and quasi-static tension test results are presented to illuminate the effect of preprocessing and ECAE route on grain size refinement and mechanical behavior. Preprocessing via rolling yielded a smaller, more homogeneous initial grain size than the conventionally extruded material. After the second processing step, ECAE, the microstructural differences due to the preprocessing methods are reduced, but not eliminated, and mechanical properties show little variation between rolling and extrusion. The ECAE route did not impact the microstructural refinement, however, the 4Bc route did lead to enhanced ductility (>36%) and higher average ultimate tensile strengths, compared to the 4A route, when tested in the normal direction (perpendicular to the ECAE extrusion direction). The relative importance of texture alteration versus grain refinement and homogeneity is highlighted herein. Lastly, we comment on the influence of processing routes on inclusions and voids.