Workability of commercial-purity titanium and 4340 steel during equal channel angular extrusion at cold-working temperatures

The deformation and failure of commercial-purity (CP) titanium (grade 2) an d AISI 4340 steel (tempered to R(c)35) during equal channel angular extrusi on were determined at temperatures between 25 degrees C and 325 degrees C a nd effective strain rates between 0.002 and 2.0 s(-1). The CP titanium allo y underwent segmented failure under all conditions except at low strain rat es and high temperatures. By contrast, the 4340 steel deformed uniformly ex cept at the highest temperature and strain rate, at which it also exhibited segmented failure. Using flow curves and fracture data from uniaxial compr ession and tension tests, workability analysis was conducted to establish t hat the failures were a result of flow localization prior to the onset of f racture. This conclusion was confirmed by metallographic examination of the failed extrusion specimens.