Vicinity Of Indentation Research Articles

Deformation Behavior and Structure of i-Al-Cu-Fe Quasicrystalline Alloy in Vicinity of Nanoindenter Indentation

The nanoindentation tests have been carried out for the quasicrystalline polygrain Al62.4Cu25.3Fe12.3 alloy with the icosahedral structure i; the load P-displacement h diagrams have been used to estimate the contributions of plastic deformation (monotonic and intermittent), and the structures of the transverse microscopic sections have been studied in the vicinity of indentations by electron microscopy. It is shown that several systems of deformation bands are formed in the elasto-plastic zone in the vicinity of the indentations along the close-packed planes of the i lattice with the five-fold and two-fold symmetry axes; the bands often begin from cracks and manifest the signs of the dislocation structure. The traces of the phase transformation with the formation of the β-phase areas are observed only in a thin layer under an indenter. The effects of intermittent deformation are up to 50% of the total inelastic deformation and are related to the plastic behavior of the quasicrystal-activation and passage of deformation bands and also the formation of undersurface micro- and nanosized cracks.

Деформационное поведение и структура квазикристаллического сплава i-Al-Cu-Fe в окрестности отпечатка наноиндентора

AbstractThe nanoindentation tests have been carried out for the quasicrystalline polygrain Al_62.4Cu_25.3Fe_12.3 alloy with the icosahedral structure i ; the load P -displacement h diagrams have been used to estimate the contributions of plastic deformation (monotonic and intermittent), and the structures of the transverse microscopic sections have been studied in the vicinity of indentations by electron microscopy. It is shown that several systems of deformation bands are formed in the elasto-plastic zone in the vicinity of the indentations along the close-packed planes of the i lattice with the five-fold and two-fold symmetry axes; the bands often begin from cracks and manifest the signs of the dislocation structure. The traces of the phase transformation with the formation of the β-phase areas are observed only in a thin layer under an indenter. The effects of intermittent deformation are up to 50% of the total inelastic deformation and are related to the plastic behavior of the quasicrystal-activation and passage of deformation bands and also the formation of undersurface micro- and nanosized cracks.

Evaluation of Local Plastic Flow in the Vicinity of Indentation by the Means of DIC Applied on SEM Micrographs

The paper presents application on digital image correlation (DIC) and microindentation for investigation of plastic flow under Brinell ball indenter applied on steel specimen made of two parts screwed together. Specimens in two different material states (a) as delivered (b) annealed were investigated. This approach enables internal surface to act as the external one and to be examined by aforementioned methods. Results obtained by application of DIC on scanning electron microscope (SEM) images are compared to microhardness maps and agreement is demonstrated.

Effect of Alloy States on the Recrystallization Behavior in Single Crystal Superalloy

Recrystallization behavior after indentation loading and heat treatment at different temperatures of the as-cast and solution-treated alloy was investigated. The results showed that slip deformation occurred in the as-cast and heat treated samples after deformation and apparent slip line can be observed. Slip lines of heat treatment state was significantly more than that of the as-cast samples. Neither equiaxed nor cellular recrystallization occurred in the surface of the as-cast and solution-treated samples after heat treatment at 1120; Slip traces were examined in the vicinity of indentation and M6C carbide precipitated on the slip line in heat-treated samples, while cellular recrystallization occurred in the internal part and MC carbides became the nucleation centers. Equiaxed recrystallization occurred simultaneously in samples of the two states with the heat treatment at 1310 after deformation and the recrystallization area increased with the processing time; after heat treatment with same time and temperature, recrystallization area of the cast samples were less than that of heat-treated samples.

Fracture behavior of CrN coatings under indentation and dynamic cycle impact

Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique (IBAMS) was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.

Indentation-induced microhardness changes in glasses: Possible fictive temperature increase caused by plastic deformation

The microhardness around a large indentation was measured for different types of glasses. In soda-lime silicate glass, a typical normal glass, the region in the immediate vicinity of the indentation was found to exhibit a lower hardness than the region far removed from the indentation. In silica glass, a typical anomalous glass, the region in the immediate vicinity of a large indentation was found to exhibit a higher hardness than the region far removed from the indentation. Asahi less brittle glass, an intermediate glass between normal and anomalous glasses, was found to exhibit little change in hardness in the vicinity of the large indentation. These findings can be explained by a deformation-induced fictive temperature increase leading to a lower hardness for soda-lime silicate glass and a higher hardness for silica glass.

Translation–rotation plasticity as basic mechanism of plastic deformation in macro-, micro- and nanoindentation processes

This paper presents a brief review of multilateral examinations for the purpose of detection of interrelation between processes occuring in solids at different levels of action of exterior loading, namely, at macro-, micro- and nanoindentation. Convincing arguments supporting the rotation deformation mechanism alongside the recognized dislocation one are adduced. It has been shown that the decrease in dislocation mobility leads at all scales to the intensification of rotation plasticity and to the involvement of other plastic deformation mechanisms, such as appearance and interaction of disclinations, twinning, phase transition and compression of material. The conversion from translation plasticity to the rotation–translation one means transition to the higher level of plastic deformation, the mesolevel, when the possibilities of the previous microscopic level are exhausted. It was established that the plastic deformation zone in the vicinity of indentations could be separated into two main specific regions: (i) peripheral region predominantly with the dislocation deformation mechanism; otherwise, translation mechanism: microlevel, and (ii) quasidestructured region mainly with the disclination or the intergranular sliding mechanism: rotation mechanism, mesolevel.

Thermal wave imaging of indented diamond coated WC

Photothermal radiometry has been used to obtain thermal wave images in the vicinity of indentations in WC–6% Ni coated with chemical vapor deposited (CVD) diamond. Features in the magnitude and phase of the thermal signal profile are consistent with a one-dimensional thermal wave theory that assumes (i) an air gap extending well beyond the visibly observable indented region, and (ii) a thermal resistance interface between the diamond film and the substrate over the entire coated surface. The theory allows us to estimate the air gap thickness, which decreases as the distance from the indented region increases. Air gap variations of tens of nanometers appear to be easily detectable.

Measurement and theory of the orientation dependence of Knoop microhardness in single-crystal mercuric iodide

Measurements were made of the orientation dependence of the Knoop microhardness H K on the (001) and (110) faces of single crystals of red (tetragonal) mercuric iodide that were vapour-grown for use in radiation detectors. The (001) faces of the crystals are softest when the major diagonal of the Knoop indentor (called here “the indentor”) is parallel to the [100] crystallographic axis, and H K increases monotonically, by about 25%, as the indentor is rotated from the [100] to the [110] axis. The (110) surfaces are hardest when the indentor is parallel to [001]; H K decreases by about 50% as the indentor is rotated from [001] to [1¯10]; the experimental data indicate an intermediate microhardness minimum that occurs before the [1¯10] orientation is reached. Particularly interesting surface topography, including bands of slip lines, is observed in the vicinity of indentations on the (110) planes, which apparently have not previously been characterized by Knoop microhardness indentation. Theoretically, the size of a microhardness indention is presumed to depend on the volume of material in which appropriate slip systems are stressed sufficiently to cause appreciable slip. To test this concept and determine which particular slip systems dominate the indention process, the “infinite flat punch” model was used to calculate the orientational and volumetric variations of shear stress on various potential slip systems in mercuric iodide. For indention processes controlled by movement (i.e. slip) of material in the [001] direction, over {100} planes, these calculations predict the following (experimentally observed) results: (a) on the (001) plane, H K is smallest at [001] and greatest at [110], with no intermediate extremum; (b) on the (110) plane, H K has its greatest value at [001] and a minimum between [001] and [1¯10]; (c) H K at [110] on the (001) plane is essentially the same as H K at [1¯10] on the (110) plane; and (d) the relative variation of H K is greater on the (110) than on the (001) surface. Finally, the expected orientational variation of H K on the (100) and (101) surfaces was determined theoretically.

Electron microscope investigation of the microplastic deformation mechanisms of silicon by indentation

The specific features of the dislocation structure, occuring in the vicinity of indentations have been studied using Si single crystals under different conditions of deformation (at temperatures of 20 to 700 °C and loadings of 0.5 to 10 p). It is shown, that the deformation of crystals at temperatures of 350 to 650 °C results in twin formation with {111} twinning plane. Flat defects with {115} habit plane are revealed. They are shown to be platelets of a new phase, which is of the hexagonal structure with c = 6.31 Å and a = 3.86 Å. The possible mechanism of the phase transformation is discussed. [Russian text ignored].