Ultrafinegrained and nanostructured materials are known to have enhanced mechanical and physical properties. One way to achieve such a microstructure is through high pressure torsion (HPT), a method of severe plastic deformation (SPD). The aim of this thesis is to investigate the evolution of microstructure und mechanical properties of two phase materials deformed by high preassure torsion. The chosen materials, both consisting of a bcc and a fcc phase are a duplexsteel and a copper-molybdenum-composit. The evolution of the microstructure and mechanical properties as a result of severe plastic deformation are investigated. Compact tension tests to evaluate the fracture toughness are carried out in three different orientations to examine the anisotropic behavior of the lamellar structure developed through the deformation process. Tensile tests are performed in one orientation but for different phase compositons in the duplex steel, originating from different deformation temperatures. In both materials aligned ultrafinegrained/nanolamellar structures are formed through co-deformation of the two phases during HPT. This results in an anisotropic fracture behaviour similar to SPD pearlite or Armco iron. In two of the three tested orientations both materials show good fracture toughness combined with high strength. In the shear direction the fracture toughness is relatively low, though still above the value of the pure Mo for the Copper Molybdenum composit and for the duplexsteel at the same level as ARMCO iron. For the duplex-steel the very small thermomechanical process window became evident during the investigations.
|Translated title of the contribution||Microstructureevolution and fracture behaviour of lamellar material produced by high pressure torsion|
|Publication status||Published - 2021|
Bibliographical noteembargoed until null
- High pressure torsion
- severe plastic deformation
- duplex steel