Shape memory effect in nanoindentation of nickel–titanium thin films

Shaw, Gordon A.; Stone, Donald S.; Johnson, A. David; Ellis, Arthur B.; Crone, Wendy C.

doi:10.1063/1.1591235

Cited by 115 publications

(74 citation statements)

References 13 publications

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“…Indentation shape recovery has also been demonstrated on the microscale [5]. Our nanoscale work shows good agreement with the microscale data, and also extends the measurements to thin film materials [6] as well as different kinds of deformation (nanoscratch and nanowear) [7]. It also indicates that shape recovery increases markedly at indentation depths less than 100nm.…”

Section: Introductionsupporting

confidence: 74%

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Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

Shaw

Crone

2003

MRS Proc.

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The mechanical properties of sputter-deposited NiTi shape memory alloy thin films ranging in thickness from 35 nm to 10 µm were examined using nanoindentation and atomic force microscopy (AFM). Indents made in films as thin as 150 nm showed partial shape recovery upon heating, although film thickness was found to have a marked effect on the results. A modified spherical cavity model is used to describe the findings, which suggest that the substrate tends block the shape memory effect as film thickness decreases below a threshold level which is specific to applied load. This has the net effect of decreasing the indent recovery below the critical film thickness. The fact that the spherical cavity model predicts the critical film thickness at which the shape memory effect is blocked indicates that the increased recovery of nanoscale indentations is due to a suppression of plastic processes rather than an enhancement of shape memory processes.

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Section: Introductionsupporting

confidence: 74%

“…According to our model [6], the radius of the region which deforms through shape memory processes, c mr , can be estimated as a function of indent depth using E = 60 GPa [10] and Y = 0.2 GPa (the critical stress for martensite twin reorientation). Likewise, c pl can be estimated using a maximum value of 0.8 GPa for Y [1].…”

Section: Q7113mentioning

confidence: 99%

Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

Shaw

Crone

2003

MRS Proc.

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“…During nanoindentation experiments, the low loads and small displacements are measured continuously, and typical load-displacement curves are recorded. Recent studies on the nanoindentation behavior of NiTi focused on characterizing the mechanical properties and transformation behavior by analyzing load-displacement data [610] and/or the residual surface features after indentation [10][11][12][13][14][15]. A widely used technique to quantify the amount of pseudoelastic recovery during nanoindentation testing is calculating the ratio of the remnant displacement h rem and the maximum displacement h max from load-displacement curves [6,16,17]: (1) Pseudoelastic recovery is characterized by low values of the remnant displacement ratio (RDR), whereas large RDR-values are associated with a more pronounced effect of plastic deformation.…”

Section: Introductionmentioning

confidence: 99%

TEM investigation of the microstructural evolution during nanoindentation of NiTi

Pfetzing

Wagner

Simon

et al. 2009

ESOMAT 2009 - 8th European Symposium on Martensitic Transformations

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Abstract. The continuous measurement of loads and displacements during nanoindentation of shape memory alloys allows a detailed investigation of pseudoelasticity on the nano-scale. However, the resulting load-displacement data simultaneously reflect several elastic and inelastic deformation processes (i.e., stress-induced martensitic transformation, plastic deformation). In the present study, we perform microstructural investigations in order to analyze the complex interactions between these mechanisms in a Ni-rich alloy. The microstructures below indents from experiments with different maximum indentation loads are characterized post-mortem by transmission electron microscopy. For small maximum indentation loads, load-displacement data exhibit considerable pseudoelastic recovery, whereas higher indentation loads are associated with a more pronounced residual deformation after unloading. These differences are clearly related to microstructural changes below the indenter tip: While both stressinduced martensitic transformation and dislocation slip occur in general, higher maximum loads are associated with an increase in plastic deformation. The corresponding higher dislocation densities impede the reverse transformation to austenite. Stabilized martensite can be observed directly below the surface for high indentation loads. Our results show that nanoindentation of NiTi allows a systematic analysis of the interaction of plastic deformation and stress induced transformation into martensite.

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“…[1][2][3][4][5][6] NiTibased shape memory films have been considered as one of the most promising candidates due to their high power output per volume, large actuation strain and high damping capacity. 7 For many micro-actuators, a narrow hysteresis is essential to improve the efficiency of actuation, whereas for energy storage devices a wide hysteresis is required.…”

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confidence: 99%

Crystal size induced reduction in thermal hysteresis of Ni-Ti-Nb shape memory thin films

Kobayashi

et al. 2016

Applied Physics Letters

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Ni41.7Ti38.8Nb19.5 shape memory alloy films were sputter-deposited onto silicon substrates and annealed at various temperatures. A narrow thermal hysteresis was obtained in the Ni-Ti-Nb films with a grain size of less than 50 nm. The small grain size, which means an increase in the volume fraction of grain boundaries, facilitates the phase transformation and reduces the hysteresis. The corresponding less transformation friction and lower heat transfer during the shear process, as well as reduced spontaneous lattice distortion, are responsible for this reduction of the thermal hysteresis.

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Shape memory effect in nanoindentation of nickel–titanium thin films

Cited by 115 publications

References 13 publications

Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

Direct Measurement of the Nanoscale Mechanical Properties of NiTi Shape Memory Alloy

TEM investigation of the microstructural evolution during nanoindentation of NiTi

Crystal size induced reduction in thermal hysteresis of Ni-Ti-Nb shape memory thin films

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