PNNL

Abstract

ZK60 Magnesium tubing has been friction extruded from as-cast billets and T5 conditioned bars using Shear Assisted Processing and Extrusion (ShAPE). Tubes having an outer diameter of 50.8 mm and wall thickness of 1.9 mm were extruded with >20 times less ram force compared to conventional extrusion due to the unique shearing conditions and tooling inherent to ShAPE. Microstructures of the as-cast billet and T5 bar feedstock materials were significantly different from each other in terms of grain size, texture, and second phase distribution; yet the resulting microstructures after ShAPE were remarkably similar. An average grain size of 4-5 microns, 20o tilt of basal texture away from the extrusion axis, and refined second phases having a uniform distribution were achieved independent of the feedstock material. Hardness for as-extruded and artificially aged tubes are presented with isotropic behavior explained by detailed microstructural analysis. This work suggests that bulk ZK60 magnesium alloys extrusions may be fabricated in a single step, with microstructures that are unobtainable with conventional extrusion.