Neutron diffraction experiments on isothermal pseudoelastic phase transformations in Cu-13.1Al- 4.0Ni (wt.%) single crystal shape memory alloys require a "stop-start" approach at different levels of strain during the austenite (A) to martensite (M) forward transformation and the M to A reverse transformation to collect diffraction data [1]. This stop-start nature of the tests has uncovered creep-like phenomena where there is stress relaxation when the forward transformation is interrupted (at constant strain) and stress recovery when the reverse transformation is interrupted (at constant strain). This material response has been confirmed by independent tests on a table-top thermomechanical tensile test machine. We also report results on strain recovery when the forward transformation is interrupted at constant stress. This type of behavior has been previously reported for Nickel-Titanium(NiTi) tubes [2] and NiTi polycrystalline wires [3]. Certain notable differences between the creep-like behavior and classical creep response of metallic alloys will be highlighted; due to these differences, we refer to the results reported here as "pseudo-creep".

Date Published: 31 March 2009
PDF: 9 pages
Proc. SPIE 7289, Behavior and Mechanics of Multifunctional Materials and Composites 2009, 72890K (31 March 2009); doi: 10.1117/12.816376

Published in SPIE Proceedings Vol. 7289:
Behavior and Mechanics of Multifunctional Materials and Composites 2009
Zoubeida Ounaies; Jiangyu Li, Editor(s)