In-situ neutron diffraction during shape-memory behavior in Fe-Mn-Si-Cr

• Published in: JOM (1989) Vol. 52; no. 10; pp. 32 - 34
• Main Authors: Tomota, Y., Harjo, S., Lukáš, P., Neov, D., Šittner, P.
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.10.2000
• Subjects: Alloys; Annealing; Heat treating; Neutrons; Shear strain; Stress concentration; Stress-strain curves; Tension tests
• ISSN: 1047-4838; 1543-1851
• DOI: 10.1007/s11837-000-0080-6

The internal stress change in the austenite matrix during shape-memory behavior in a ferrous alloy was examined by means of an in situ neutron diffraction technique. After tensile deformation accompanying the austenite to epsilon martensite transformation, the internal stress is yielded. The averaged internal elastic strain in < 111 > oriented austenite grains was measured. The internal stress remained after tensile straining and decreased after subsequent reverse transformation on heating, i.e., shape recovery process. When the tensiele straining and subsequent annealing was performed repeatedly, which is a kind of "training", the measured recovery strain increased and stress-induced transformation started at a lower applied stress in subsequent cycles. These findings suggest that a key point for improving the shape-memory effect is to increase the ability of the alloy to accumulate oriented internal stress generated by the martensitic transformation.