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Ohmura, Takahito; Tsuzaki, Kaneaki

doi:10.2320/materia.46.251

Cited by 12 publications

(3 citation statements)

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“…It can be called depth-sensing indentation, based on the measurement principle. Details of the principles of this technique are available in the literature [2][3][4][5][6][7][8][9][10][11][12][13]. The nanoindentation technique is just on the milestone of the 30-year anniversary of the publication of the landmark paper by Oliver and Pharr in 1992 [7].…”

Section: Introductionmentioning

confidence: 99%

Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

Ohmura

Wakeda

2021

Materials

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The attractive strain burst phenomenon, so-called “pop-in”, during indentation-induced deformation at a very small scale is discussed as a fundamental deformation behavior in various materials. The nanoindentation technique can probe a mechanical response to a very low applied load, and the behavior can be mechanically and physically analyzed. The pop-in phenomenon can be understood as incipient plasticity under an indentation load, and dislocation nucleation at a small volume is a major mechanism for the event. Experimental and computational studies of the pop-in phenomenon are reviewed in terms of pioneering discovery, experimental clarification, physical modeling in the thermally activated process, crystal plasticity, effects of pre-existing lattice defects including dislocations, in-solution alloying elements, and grain boundaries, as well as atomistic modeling in computational simulation. The related non-dislocation behaviors are also discussed in a shear transformation zone in bulk metallic glass materials and phase transformation in semiconductors and metals. A future perspective from both engineering and scientific views is finally provided for further interpretation of the mechanical behaviors of materials.

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Section: Introductionmentioning

confidence: 99%

Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

Ohmura

Wakeda

2021

Materials

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“…Nanoindentation is a technique for measuring the mechanical response of a material to indentation by a pyramidal or other type of indenter into a local region of a material surface under control with load resolution of µN and displacement resolution of nm. 6,7) Addition of the function of a probe microscope (Scanning Probe Microscope, SPM), which scans the sample surface with an indenter used for indentation, makes it possible to select arbitrary positions such as just above the grain boundary or in the vicinity of the grain boundary with high spatial resolution of about 10 nm, enabling evaluation of the plasticity resistance of individual grain boundaries. It is also possible to obtain crystallographic information for each grain by using electron back scattering diffraction (EBSD) measurement, and to discuss the effect of the dynamic condition and geometric factors under the external force at each grain boundary.…”

Section: Introductionmentioning

confidence: 99%

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Endoh¹,

Kimura

et al. 2021

Mater. Trans.

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Nanoindentation measurements on various grain boundaries were performed to clarify the effects of the geometry of neighboring grains and the addition of boron (B) on plasticity resistance in the vicinity of grain boundaries in interstitial free (IF) steels. We define a parameter, ¡, which is measured by the slope of a P/hh curve with load, P, and displacement, h, to estimate the resistance against plastic deformation in the grain interior and at the grain boundaries. The value of ¡ is almost constant with the geometric compatibility factor of the grain boundaries. This result shows that the geometry of the neighboring grains does not affect the plasticity resistance of the grain boundaries. However, the value of ¡ increases by the addition of B due to the segregation of B and Ti to the grain boundaries. It is indicated that the elemental segregation to the grain boundaries enhances the resistance to the plastic deformation in the vicinity of the grain boundaries.

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“…It can be called, in particular, depth-sensing indentation, based on the measurement principle. The details of this technique are available in the literature Kinoshita 1997, 1978;Newey et al 1982;Loubet et al 1984;Doerner and Nix 1986;Oliver and Pharr 1992;Tsui et al 1996;Bolshakov and Pharr 1998;Lim and Chaudhri 1999;Nix and Gao 1998;McElhaney et al 1998;Ohmura and Tsuzaki 2007a).…”

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confidence: 99%

Nanomechanical Characterization of Metallic Materials

Ohmura

2022

The Plaston Concept

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Mechanical behavior of metallic materials on nanoscale is characterized by using Nanoindentation and Transmission Electron Microscope (TEM) to understand the fundamental plasticity mechanisms associated with microstructural factors including dislocations. The advanced characterization techniques enable us to grasp the behavior on the nanoscale in detail. New knowledges are obtained for the plasticity initiation under the extremely high stress close to the theoretical strength in regions with defect-free matrix and pre-existing defects such as grain boundaries, in-solution elements, and dislocations. The grain boundaries act as an effective dislocation source, the in-solution elements retard a nucleation of dislocation, and the pre-existing dislocations assist a plasticity initiation. The deformation behavior associated with microstructures is also described. The dislocation structure with a certain density was observed right after indentation-induced strain burst, which is so-called “pop-in,” suggesting a dislocation avalanche upon the pop-in. It has been directly observed that the lower mobility screw dislocation causes the higher flow stress in a bcc metal. A remarkable strain softening can be understood by an increase in dislocation density based on conventional physical models. Phase stability for indentation-induced transformation depends on a constraint effect by inter-phase boundary and grain boundary.

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Cited by 12 publications

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Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Nanomechanical Characterization of Metallic Materials

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