NOVEL FERROMAGNETIC MATERIALS WITH IMPROVED MECHANICAL PERFORMANCE

<p>"The ductility of intermetallics has long been a hindrance to their broad adaptation despite a significant range of properties such as magnetic, half-metallic, and shape memory behavior. The lack of a general theory for the ductility of intermetallics along with the lack of prior art that experimentally measured mechanical properties drives the need for significant investment in many of these novel magnetic materials in order to even understand, let alone correct, poor ductility.</p> <p>This dissertation includes work that explored the effect of vanadium content and quenching rate on the microstructure and ductility of Fe-Co alloys. Results indicated that a martensitic transformation was responsible for the observed property changes with additions of vanadium as low as 1.77 at. % and at cooling rates as slow as 0.167 °C/s.</p> <p>A novel technique for predicting the ductility of intermetallics through the use of density functional theory calculations was developed to explain the observed improvements with vanadium additions. The model predicts, and experiments validate, that improved ductility in Fe-Co alloys occurs because vanadium additions drive changes in the anti-phase boundary energies which enable easier cross-slip and thus a shift in fracture mode to transgranular cleavage.</p> <p>Finally, the developed intermetallic ductility model was applied to the inverse Huesler alloy Mn₂CoAl. Results indicated that Mn₂CoAl is brittle. Changes in stoichiometry were predicted to enable changes in the anti-phase boundary energies and cross-slip energies, but these changes are not sufficient to overcome the driving force for intergranular fracture"--Abstract, p. iv</p>

Name thesis:degree_name

Ph. D. in Materials Science and Engineering

Grantor

Missouri University of Science and Technology

Author dc:creator

• Everhart, Wesley Alexander

• Materials Science and Engineering

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/3248

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-4253