Microscopic and macroscopic analyses of the interaction mechanism between defect growth and dislocation emission in single‐crystal aluminum

2021 ◽  
Author(s):  
Xiaotao Li ◽  
Shenyou Peng ◽  
Xu Zhang ◽  
Xiaoyu Jiang ◽  
Qingyuan Wang
Keyword(s):  
Single Crystal ◽  
Interaction Mechanism ◽  
Dislocation Emission ◽  
Defect Growth

Nanoindentation Studies of Yield Point Phenomena on Gold Single Crystals

1996 ◽  
Vol 436 ◽  
Author(s):  
S. G. Corcoran ◽  
R. J. Colton ◽  
E. T. Lilleodden ◽  
W. W. Gerberich
Keyword(s):  
Single Crystal ◽  
Dislocation Nucleation ◽  
Dislocation Emission ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Slip Bands ◽  
Contamination Effect ◽  
Order Of Magnitude ◽  
Dislocation Spacing

AbstractNanoindentation studies often show an instantaneous displacement-excursion in the loaddisplacement curve. This anomaly is generally associated with a surface contamination effect, dislocation emission, a phase transition, or an oxide break-through event. The determination of which effect is operative is often difficult when investigating oxide covered surfaces. We have performed a detailed nanoindentation study on clean, flame annealed single-crystal Au thus eliminating the effects of a surface oxide or contamination layer. Multiple displacement excursions were observed exhibiting a new phenomenon of “staircase” yielding. Owing to the fact that our radius of contact is more than an order of magnitude smaller than the average dislocation spacing expected for well annealed Au, the excursions are explained in terms of multiple dislocation nucleation events on parallel slip bands. Indentation data were taken on Au (111), (110), and (100) single crystal surfaces.

Fundamental Aspects of Friction and Wear Contacts in Surfaces

2000 ◽  
Vol 649 ◽  
Author(s):  
William W. Gerberich ◽  
Natalia I. Tymiak ◽  
Donald E. Kramer
Keyword(s):  
Transition Metals ◽  
Single Crystal ◽  
Friction And Wear ◽  
Dislocation Motion ◽  
Sliding Contact ◽  
Quasi Equilibrium ◽  
Dislocation Emission ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Pile Up

ABSTRACTUnexpected friction and wear transitions occur in transition metals associated with dislocation emission, dislocation storage, and oxide break-through phenomena. Both normal nanoindentation and nanoscratch evaluations of conical diamond tips driven into tungsten {100} single crystal surfaces have been conducted. In terms of initiating plasticity undert the contact, this represents a high Peierl's barrier for dislocation motion in transition metals. Both quasi-equilibrium and kinetic aspects are reported along with current but speculative ideas on multiple friction and wear transitions. Preliminary results show that yielding under contacts can produce a 250 nm displacement excursion. Ramifications are seen in terms of friction coefficients which can double during the near-instantaneous yield excursion but then continue to triple from about 0.05 to 0.15 in the pile-up phase in front of the sliding contact. Implications of how nanotribological issues such as adhesion connect through this mesoscale activity to macroscopic friction and wear are discussed.

scholarly journals Fracture Toughness Estimation of Single-Crystal Aluminum at Nanoscale

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 680
Author(s):  
Wilmer Velilla-Díaz ◽  
Luis Ricardo ◽  
Argemiro Palencia ◽  
Habib R. Zambrano
Keyword(s):  
Molecular Dynamics ◽  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Single Crystal ◽  
Fracture Behavior ◽  
Published Data ◽  
Dislocation Emission ◽  
Fracture Simulation ◽  
Dynamics Simulations ◽  
Nano Crystal

In this publication, molecular dynamics simulations are used to investigate the fracture behavior of single-crystal aluminum. The stress intensity factor is estimated by means of four different methods, the accuracy is assessed for each approach and the fracture toughness is estimated. The proposed methodology is also applied to estimate the fracture toughness for graphene and diamond using published data from other scientific articles. The obtained fracture toughness for the single-crystal aluminum is compared with other nanomaterials that have similar microstructures. Dislocation emission during the fracture simulation of the cracked nano-crystal of aluminum is analyzed to study the fracture behavior. Brittle fracture behavior is the predominant failure mode for the nanomaterials studied in this research.

Slip systems and dislocation emission from crack tips in single crystal TiC at low temperatures

1996 ◽  
Vol 44 (6) ◽  
pp. 2265-2283 ◽  
Author(s):  
F.R. Chien ◽  
X.J. Ning ◽  
A.H. Heuer
Keyword(s):  
Single Crystal ◽  
Low Temperatures ◽  
Slip Systems ◽  
Dislocation Emission ◽  
Crack Tips

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

Dislocations, Ordering and Antiferromagnetic Domains in MnO

1970 ◽  
Vol 28 ◽  
pp. 522-523
Author(s):  
D. J. Barber ◽  
R. G. Evans
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Optical Microscopy ◽  
Defect Chemistry ◽  
Magnetic Structures ◽  
Optically Transparent ◽  
Magnetic Features ◽  
Antiferromagnetic Domains

Manganese (II) oxide, MnO, in common with CoO, NiO and FeO, possesses the NaCl structure and shows antiferromagnetism below its Neel point, Tn∼ 122 K. However, the defect chemistry of the four oxides is different and the magnetic structures are not identical. The non-stoichiometry in MnO2 small (∼2%) and below the Tn the spins lie in (111) planes. Previous work reported observations of magnetic features in CoO and NiO. The aim of our work was to find explanations for certain resonance results on antiferromagnetic MnO.Foils of single crystal MnO were prepared from shaped discs by dissolution in a mixture of HCl and HNO3. Optical microscopy revealed that the etch-pitted foils contained cruciform-shaped precipitates, often thick and proud of the surface but red-colored when optically transparent (MnO is green). Electron diffraction and probe microanalysis indicated that the precipitates were Mn2O3, in contrast with recent findings of Co3O4 in CoO.

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

1974 ◽  
Vol 32 ◽  
pp. 506-507 ◽  
Author(s):  
J. M. Galbraith ◽  
L. E. Murr ◽  
A. L. Stevens
Keyword(s):  
Electron Microscopy ◽  
Wave Propagation ◽  
Structural Change ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Shock Loading ◽  
Slip Systems ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

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