Deformation and Toughness of α-Silicon Nitride Single Crystals

1992 ◽  
Vol 287 ◽  
Author(s):  
H. Suematsu ◽  
J. J. Petrovic ◽  
T. E. Mitchell
Keyword(s):  
Silicon Nitride ◽  
Single Crystals ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Statistical Variations ◽  
Knoop Indentation ◽  
Primary Slip System ◽  
Indentation Methods

ABSTRACTVickers and Knoop indentation methods were used to determine the deformation behavior and fracture toughness of single crystal α-Si3N4 at room temperature. The tests were performed on (0001), (1100) and (1120) faces; both hardness and toughness values were found to be independent of orientation within statistical variations. Thus, the mechanical properties of silicon nitride are essentially isotropic at room temperature.Single crystals of α-Si3N4 were also compressed at 1760 and 1820°C at a strain rate of The sample tested at 1760°C showed yielding at a stress of 200MPa but it fractured before indicating a significant amount of plastic deformation. On the other hand, the sample compressed at 1820°C deformed to a strain of 2.7% at a stress of 4OMPa before fracturing. A significant density of dislocations was observed by transmission electron microscopy. From conventional g.b analysis, the Burgers vector of the dislocations was determined to be 1/3<1120>. From the line direction of the dislocations, the primary slip system of α-Si3N4 is determined to be {1101}<1120>.

Plastic Deformation of Mo(Si,Al)2 Single Crystals with the C40 Structure

1996 ◽  
Vol 460 ◽  
Author(s):  
M. Moriwaki ◽  
K. Ito ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Single Crystals ◽  
Deformation Behavior ◽  
Basal Slip ◽  
Room Temperature ◽  
Slip Systems ◽  
Temperature Range ◽  
Al Content ◽  
Partial Dislocations ◽  
Increasing Temperature ◽  
Critical Resolved Shear Stress

ABSTRACTThe deformation behavior of single crystals of Mo(Si,Al)2 with the C40 structure has been studied as a function of crystal orientation and Al content in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only above 1100°C for orientations where slip along <1120> on (0001) is operative and no other slip systems are observed over whole temperature range investigated. The critical resolved shear stress for basal slip decreases rapidly with increasing temperature and the Schmid law is valid. Basal slip appears to occur through a synchroshear mechanism, in which a-dislocations (b=1/3<1120>) dissociate into two synchro-partial dislocations with the identical Burgers vector(b*1/6<1120>) and each synchro-partial further dissociates into two partials on two adjacent planes.

OS0125 Deformation behavior of magnesium single crystals above room temperature

2014 ◽  
Vol 2014 (0) ◽  
pp. _OS0125-1_-_OS0125-2_
Author(s):  
Shinji ANDO ◽  
Kazuki FUKUSHIMA ◽  
Masayuki TSUSHIDA ◽  
Hiromoto KITAHARA
Keyword(s):  
Single Crystals ◽  
Deformation Behavior ◽  
Room Temperature

Microstructural Investigations of the Unusual Deformation Behavior of Nb2Co7

2008 ◽  
Vol 1128 ◽  
Author(s):  
Frank Stein ◽  
Martin Palm ◽  
Georg Frommeyer ◽  
Padam Jain ◽  
Sharvan Kumar ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
Room Temperature ◽  
Single Phase ◽  
Intermetallic Phase ◽  
Shear Bands ◽  
Bulk Sample ◽  
Strain Rates ◽  
Bending Tests ◽  
Optical Scanning ◽  
Transmission Electron

AbstractUsually, single-phase intermetallics in bulk form can easily be crushed into powder by hammering. It was therefore quite a surprise when we found that a bulk sample of the monoclinic intermetallic compound Nb2Co7 could be extensively deformed at room temperature without shattering or fracturing. In a previous paper, results of microhardness, compression, tensile and bending tests were provided and discussed [1]. In order to understand the observed unusual deformation behavior of this intermetallic phase, its hitherto unknown crystal structure has been studied and the microstructure of undeformed and deformed samples has been analyzed in the present investigation by light-optical, scanning electron and transmission electron microscopy. Single-phase specimens deformed at very different strain rates (hammering and conventional compression testing) both show the occurrence of microcracks along grain boundaries which, in compression-deformed specimens, are strongly localized in extended shear bands oriented approximately 45° to the compression axis. The grains adjacent to the microcracks are heavily deformed whereas, away from the sheared regions, the samples remain free of any indication of plastic deformation.

The Charge State of Iron Ions Implanted Into Sapphire

1988 ◽  
Vol 100 ◽  
Author(s):  
C. J. Mchargue ◽  
P. S. Sklad ◽  
C. W. White ◽  
G. C. Farlow ◽  
A. Perez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Charge State ◽  
Room Temperature ◽  
Local Environment ◽  
Rutherford Backscattering ◽  
Iron Ions ◽  
Valence States ◽  
Transmission Electron

ABSTRACTSingle crystals of α-Al2O3 were implanted with 57Fe+ at room temperature to fluences ranging from 1016 to 1017 ions/cm2. The damage in the implanted zone and the valence states and local environment of implanted ions were studied by transmission electron microscopy, Rutherford backscattering-channelling, and conversion electron Mössbauer spectroscopy. The implanted iron was distributed among the three charge states Fe2+, Fe3+, and Fe°(metallic clusters) with the relative amount of each varying with concentration of implanted iron.

Crack propagation and deformation behavior of Al2O3-24 vol. % ZrO2 composite studied by transmission electron microscopy

1994 ◽  
Vol 9 (5) ◽  
pp. 1199-1207 ◽  
Author(s):  
Byong-Taek Lee ◽  
Kenji Hiraga
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Crack Propagation ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Transmission Electron ◽  
Boundary Sliding ◽  
Increasing Temperature ◽  
Indentation Site

Crack propagation and deformation behavior of a pressureless-sintered Al2O3-24 vol. % ZrO2 composite have been studied by transmission electron microscopy on Vickers-indented specimens from room temperature to 1200 °C. Hardness of the composite gradually decreases with increasing temperature, whereas the ratio of indent to crack lengths, which corresponds to the apparent toughness of materials, decreases up to about 1000 °C and then quickly increases with increasing temperature. In the samples indented at room temperature and 1000 °C, most of the cracks propagate along Al2O3/ZrO2 interfaces and Al2O3 grain boundaries, but a few monoclinic ZrO2 grains are transgranularly fractured. These fractured grains are heavily deformed and produce a marked reduction of the driving force for propagation of cracks at room temperature. In the sample indented at 1200 °C, cracks are hardly observed, but on the other hand, formation of subgrain boundaries, elongation of grains, and grain boundary sliding are observed both in the Al2O3 and ZrO2 grains located around the indentation site.

Indentation-Induced Deformation Behavior in Martensitic Steel Observed through In Situ Nanoindentation in a Transmission Electron Microscopy

2006 ◽  
Vol 503-504 ◽  
pp. 239-244 ◽  
Author(s):  
Takahito Ohmura ◽  
A. Minor ◽  
Kaneaki Tsuzaki ◽  
J.W. Morris
Keyword(s):  
Grain Boundary ◽  
Deformation Behavior ◽  
Critical Stress ◽  
Martensitic Steel ◽  
High Angle ◽  
Block Boundary ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Pile Up

Deformation behavior in the vicinity of grain boundary in Fe-0.4wt%C tempered martensitic steel were studied through in-situ nanoindentation in a TEM. Two types of boundaries were imaged in the dislocated martensitic structure: a low-angle lath boundary and a high-angle block boundary. In the case of a low-angle grain boundary, the dislocations induced by the indenter piled up against the boundary. As the indenter penetrated further, a critical stress appears to have been reached and a high density of dislocations was suddenly emitted on the far side of the grain boundary into the adjacent grain. In the case of the high-angle grain boundary, the numerous dislocations that were produced by the indentation were simply absorbed into the boundary, with no indication of pile-up or the transmission of strain.

A Transmission Electron Microscope Study of Hardness Indentations in MoSi2

2000 ◽  
Vol 15 (4) ◽  
pp. 1025-1032 ◽  
Author(s):  
P. H. Boldt ◽  
G. C. Weatherly ◽  
J. D. Embury
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Slip Systems ◽  
Cavity Model ◽  
Dislocation Loops ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Large Rotations ◽  
Transmission Electron Microscope Study

Transmission electron microscopy and electron diffraction were used to study hardness indentations made at room temperature in ⟨001⟩-oriented single crystals of MoSi2. Two families of slip systems, {110}⟨001⟩ and {101}⟨010⟩, were identified. The first system formed ⟨001⟩ dislocation loops by prismatic punching beneath the indenter, while the second system led to large rotations of the crystal lattice beneath the indenter. The lattice rotations were used to estimate the density of dislocations stored in this volume. The results demonstrate that the hardness response of MoSi2 can be explained by the expanding cavity model with most of the plastic accommodation occurring immediately beneath the indenter.

Soft and Hard Modes of Deformation in Mosi2 Single Crystals

1994 ◽  
Vol 364 ◽  
Author(s):  
K. Ito ◽  
T. Yano ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Single Crystals ◽  
Plastic Flow ◽  
Deformation Behavior ◽  
Crystal Orientation ◽  
Room Temperature ◽  
Intermediate Temperature ◽  
Slip Systems ◽  
Anomalous Increase ◽  
Temperature Range ◽  
Intermediate Temperature Range

AbstractThe deformation behavior of MoSi2 single crystals has been studied in the temperature range of -196<1500°C. While [001]-oriented crystals can be plastically deformed only above 1300°C, plastic flow is possible from temperatures as low as room temperature for single crystals with orientations other than [001]. Five slip systems, {110)<111], {011)<100], {010)<100], {023)<100] and {013)<331], are identified to be operative, depending on crystal orientation. An anomalous increase in CRSS is observed in the intermediate temperature range for the former three slip systems. Schmid’s law is generally valid for the soft modes, {110)<111], {011)<100] and {023)<100]. In contrast, the CRSS for the hard mode, {013)<331], strongly depends on crystal orientation with the higher values for orientations closer to [001].

A Weak-Beam Study of the Microstructure of β-CUZN Deformed in the Domain of Flow Stress Anomaly

1988 ◽  
Vol 133 ◽  
Author(s):  
G. Dirras ◽  
P. Beauchamp ◽  
P. Veyssière
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Burgers Vector ◽  
Weak Beam ◽  
Transmission Electron ◽  
Edge Component ◽  
Imaging Conditions

ABSTRACTβ-brass single crystals oriented along <001> were deformed between room temperature and 300°C. The deformation microstructure and dissociation properties were studied by transmission electron microscopy under weak-beam imaging conditions.Whatever the deformation temperature, superdislocations with <111> Burgers vector and strong edge component dominate within the microstructure. In addition, below the temperature of the flow stress peak (≈ 250°C), the density of screw relative to mixed superdislocations decreases as straining temperature increases. Dissociation does not always occur on the slip plane neither does it proceed exclusively by glide, even in samples deformed at 100°C.

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