Nanomechanical Properties of Ni-Mn-Ga

Document Type

Student Presentation

Presentation Date


Faculty Sponsor

Chad Watson


Ni-Mn-Ga, a ferromagnetic shape-memory alloy, changes shape upon the application of a variable magnetic field. This behavior is of interest for nanoscale applications, including actuators and memory devices. The shape-memory behavior of Ni-Mn-Ga is facilitated by magnetic field- or mechanical stress-induced twin boundary motion. Understanding the constraints, magnitude and mechanisms of stress-induced twinning and magnetization at small length scales are critical for developing nanoscale technology. Thus, this work focuses on the evaluation of nanomechanical properties, through instrumented indentation, of Ni-Mn-Ga single crystals as a function of crystallographic c orientation. The reduced elastic modulus and load-displacement behavior was characterized for c in-plane and out-of-plane. Preliminary results show that the reduced elastic modulus for out-of-plane (124 ± 5 GPa) was 33% greater than in-plane (93 ± 3 GPa). Load-displacement curves from indentations on in-plane regions exhibit greater non-linear recovery during unloading compared to out-of-plane regions. Based on these results, the alignment of the c-axis plays role in the deformation behavior of Ni-Mn-Ga. This role may be attributed to differences in nanoscale twinning behavior, which will be presented.

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