Improvement of mechanical properties of magnesium alloy ZK60 by integrated extrusion and equal channel angular pressing

The paper demonstrates the feasibility of upscaling of severe plastic deformation (SPD) techniques using an integrated process that combines conventional extrusion and equal channel angular pressing in a single processing step. The process was applied for production of magnesium ZK60 bars 16 mm in diameter and up to 4 m in length. The processed material exhibited an excellent balance of strength and tensile ductility. It had a yield strength of 310 MPa and the ultimate tensile strength of 351 MPa. The total elongation of 17.1% was about 2.5 times and the reduction in area of 42.5% was more than 10 times larger than the corresponding values in the as-received condition. A transition from brittle to ductile fracture suggesting a change in the deformation mechanisms was also found in the material processed by the integrated SPD technique. Analysis of microstructure and texture of the SPD-processed bars showed that this excellent combination of strength and ductility can be attributed to the synergy of fine-grained microstructure and favorable texture promoting basal slip (in concert with non-basal slip), yet not to an extent that strength is sacrificed. The possibility to produce long bars of ZK60 with exceptionally good mechanical properties in a “semi-continuous” process is a promising opportunity for the transfer of severe plastic deformation processing to industrial manufacturing scale.