Mechano-Electrochemistry of Nickel Titanium Alloy

Abstract

MECHANICAL ENGINEERING

Mechano-Electrochemistry of Nickel Titanium Alloy

Deanna Schauben

Thesis under the direction of Professor Cary L. Pint

The fields of strain engineering and mechano-electrochemistry have recently emerged to explore the relationship between strain and electrochemical properties, particularly as they pertain to corrosion. NiTi is an ideal candidate for investigating this relationship due to its superelastic and shape memory properties. Here, an in-situ mechano-electrochemical cell is designed and implemented to obtain the open circuit voltage response of NiTi during straining. Of particular interest is the OCV behavior during the stress-induced martensitic transformation, which is both immediate and dramatic. A survey of OCV response during straining as well as the steady-state response after straining was performed for samples deformed to different percentages of strain at two different strain rates. The steady-state response is permanently changed by up to 44.8 mV only when strain is halted within the SIM plateau, and the magnitude of OCV change increases by a factor of about 2.5-2.9 with a strain rate increase by a factor of 5. These results point to an energetic mechanism of the SIM transformation that is yet to be investigated.