Assessment of equal channel angular extrusion processing of magnesium alloys

Equal channel angular extrusion (ECAE) offers the potential to introduce very large strains into a metal workpiece without changing its cross-section. Hence, it could be an attractive technique for developing a fine-grained forging stock with good forming characteristics. Magnesium alloys are ideal candidates to benefit from the ECAE technique, because of their poor forming characteristics due to a hexagonal close packed crystal structure and a low melting point, which allows them to be ECAE processed isothermally at temperatures of 300°C and below. An assessment of the technique has been made with the alloys AZ31B and ZK60. The mechanical properties of AZ31B are largely unaffected by the process, however, the ZK60 alloy responds favorably. Relative to the as-received material, the ductility is improved by 2 to 3 times over the entire temperature range investigated (24 - 450°C). Explanations for the property enhancements are discussed in terms of microstructure observations and deformation mechanisms.