Hot forming of shape memory alloys in steel shells: formability, interface, bonding quality

• Published in: Production engineering (Berlin, Germany) Vol. 15; no. 2; pp. 271 - 283
• Main Authors: Gerstein, Gregory, Kahra, Christoph, Golovko, Oleksandr, Schäfke, Florian, Klose, Christian, Herbst, Sebastian, Nürnberger, Florian, Maier, Hans Jürgen
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-04-2021; Springer Nature B.V
• Subjects: Engineering; Extrusion; Ferritic stainless steels; Formability; Hot forming; Hot rolling; Industrial and Production Engineering; Metal forming; Metallurgy; Oxidation; Production; Production Process; Shape memory alloys; Tensile tests; Hot deformation; Metallurgical bonding; SMA; Rolling; Extrusion; Hot tensile tests; Steel shell; Upsetting
• ISSN: 0944-6524; 1863-7353
• DOI: 10.1007/s11740-021-01024-8

Metal forming of shape memory alloys (SMA) can be challenging since these are very often brittle due to their intermetallic character. However, formability is often needed not only for realising the desired geometry but also for tailoring the microstructure and the functional properties. To investigate whether the encapsulation in a steel shell can improve the formability of shape memory alloys, Co
49
Ni
21
Ga
30
and Ni
49.5
Fe
14.5
Mn
4.0
Ga
26.0
Co
6.0
samples were subjected to tensile tests, upsetting, rolling and extrusion. A ferritic steel (1.0503) was used as the shell material. The shell was employed to curtail the formation of tensile stresses in the core, to maintain high temperatures during processing and to prevent oxidation. With this approach, not only forming of the SMA in the steel shell was possible but also an intensive metallurgical bond between the SMA and the steel shell can be achieved during hot rolling or extrusion.