Formability and Strain Localizations in Ultrafine Grained HSLA Steel Processed by High Pressure TorsionThursday (29.09.2016) 16:15 - 16:30 Part of:
A key aspect of severe plastic deformation (SPD) processes is the invariant sample geometry which requires subsequent processing steps such as forming to generate the final product shape. Ultrafine grained materials are known for their combination of high strength and ductile behavior, yet they typically lack strain hardening capability which makes them prone to strain localizations. The present work focuses on the formability and forming behavior of an ultrafine grained high strength low alloy (HSLA) steel processed by high pressure torsion. Furthermore, the effect of heat treatments as a potential method to improve the formability is also investigated. Under uniaxial tension the as processed condition shows a ductile behavior with high post-necking-elongation whereas brittle fracture occurs after a recovery annealing. This is contrary to the behavior under 3-point-bending where brittle shear fracture occurs for the as processed condition and the formability improves significantly after recovery annealing. These results will be discussed with respect to dislocation source hardening effects and damage induced during SPD processing.