Scaled-Up Fabrication of Thin-Walled ZK60 Tubing Using Shear Assisted Processing and Extrusion (ShAPE)

摘要

Shear Assisted Processing and Extrusion (ShAPE) has been scaled-up and applied to direct extrusion of thin-walled magnesium tubing. Using ShAPE, billets of ZK60A-T5 were directly extruded into round tubes having an outer diameter of 50.8 mm and wall thickness of 1.52 mm (extrusion ratio of 17.7). Due to material flow effects resulting from the simultaneous linear and rotational shear intrinsic to ShAPE, the ram force and k-factor during extrusion were just 40 kN (9000 lb_f) and 3.33 MPa (0.483 ksi) respectively. This represents a >10 times reduction in k-factor, and therefore ram force, compared to conventional extrusion. The severe shearing conditions inherent to ShAPE resulted in microstructural refinement with an average grain size of 3.8 μm measured at the midpoint of the tube wall. Tensile testing per ATSM E-8 on specimens oriented parallel to the extrusion direction gave an ultimate tensile strength of 254.4 MPa and elongation of 20.1%. Specimens tested perpendicular to the extrusion direction had an ultimate tensile strength of 297.2 MPa and elongation of 25.0%.