Nanoscale Pseudoelasticity of Single-crystal Cu–Al–Ni shape-memory Alloy Induced by Cyclic Nanoindentation
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Shape-memory alloys (SMA) have become important structural materials of dynamic microsystems and bioimplants because of their ability to undergo large reversible strains (typically ∼8%) by shear dominated, thermoelastic, displacive phase transformations and crystallographic twinning processes. Advances in nanotechnology and microelectromechanical devices have turned the research attention to nanoscale material behavior. Single-crystal Cu–Al–Ni alloy exhibits the largest reversible strain (e.g., 17%) among SMA as well as high thermal and electrical conductivity [1, 2, 3]. In addition to the common type of pseudoelasticity associated with phase transformation from the high-temperature austenite (parent) phase to the low-temperature martensite (derivative) phase and vice versa, Cu–Al–Ni demonstrate another type of pseudoelastic behavior involving only martensitic transformations without the formation of austenite.
Previous studies have provided valuable information about phase...
KeywordsAustenite Martensite Phase Transformation Contact Depth Nanoindentation Experiment
The authors gratefully acknowledge Dr. A. D. Johnson for helpful discussions and Professor N. Balsara at the University of California at Berkeley for the use of the differential scanning calorimetry equipment.
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