Mechanical properties of GaAs crystals

1987 ◽  
Vol 2 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Ichiro Yonenaga ◽  
Utako Onose ◽  
Koji Sumino
Keyword(s):  
Mechanical Properties ◽  
Surface Condition ◽  
Gaas Crystal ◽  
Compression Tests ◽  
Czochralski Technique ◽  
Lower Yield ◽  
Temperature Range ◽  
Defect Complexes ◽  
Transmission Electron ◽  
Effective Generation

Mechanical properties of GaAs crystals grown by the liquid encapsulated Czochralski technique and the boat technique are investigated by means of compression tests. Stressstrain characteristics of a GaAs crystal in the temperature range 400°–500°C are very similar to those of a Si crystal in the temperature range 800°–900°C. This seems to reflect the fact that the dislocation mobility in a GaAs crystal in the former temperature range is comparable to that in a Si crystal in the latter temperature range. Dislocations in GaAs crystals are found to be easily immobilized at an intermediate temperature due to gettering of impurities and/or impurity-point defect complexes. In comparison to a Si crystal, the surface of a GaAs crystal seems to involve irregularities that act easily as effective generation centers for dislocations. Thus the magnitude of the yield stress of an aged GaAs crystal is controlled by the surface condition and is not influenced by the density of dislocations involved in the crystal. The socalled steady state of deformation is realized in a GaAs crystal in the deformation stage after the lower yield point as in Si and Ge crystals. Dislocation distributions in a deformed GaAs crystal observed by transmission electron microscopy is very similar to those in deformed Si and Ge crystals.

Mechanical properties and dislocation dynamics of GaP

1989 ◽  
Vol 4 (2) ◽  
pp. 355-360 ◽  
Author(s):  
Ichiro Yonenaga ◽  
Koji Sumino
Keyword(s):  
Mechanical Properties ◽  
Dislocation Dynamics ◽  
Dynamic State ◽  
Strain Rates ◽  
Compression Tests ◽  
Stress Strain ◽  
Temperature Range ◽  
Strain Behavior ◽  
Defect Complexes ◽  
Impurity Defect

Mechanical properties of GaP crystals are investigated in the temperature range 600–900 °C by means of compression tests. Stress-strain characteristics of a GaP crystal in the temperature range 600–800 °C are very similar to those of a GaAs crystal in the temperature range 450–600 °C. The dynamic state of dislocations during deformation is determined by means of the strain-rate cycling technique. The deformation of GaP is found to be controlled by the dislocation processes the same as those in other kinds of semiconductors such as Si, Ge, and GaAs. The velocity v of dislocations that control deformation is deduced to be v = v0 τ exp(–2.2 eV/kT) as a function of the stress τ and the temperature T, where v0 is a constant and k the Boltzmann constant. The Portevin-LeChatelier effect is observed in the stress-strain behavior in the deformation at high temperatures and under low strain rates, which may be attributed to the locking of dislocations by impurities or impurity-defect complexes.

Effect of oxidation on the mechanical properties of a NbAl3 alloy at intermediate temperatures

1992 ◽  
Vol 7 (12) ◽  
pp. 3219-3234 ◽  
Author(s):  
S.V. Raj ◽  
M. Hebsur ◽  
I.E. Locci ◽  
J. Doychak
Keyword(s):  
Mechanical Properties ◽  
Incubation Period ◽  
Surface Condition ◽  
Constant Load ◽  
Compression Tests ◽  
Cross Sectional ◽  
The Matrix ◽  
Oxide Spalling ◽  
Load Tests ◽  
Microstructural Examination

Although a NbAl3 alloy containing Cr, W, and Y has excellent oxidation resistance above 1440 K, it suffers from severe environmental attack during deformation at intermediate temperatures between 900 and 1100 K. Specimens tested in constant velocity and constant load direct compression tests showed varying degrees of degradation depending on environment (i.e., air or argon), surface finish, stress, and temperature. As a result, there were corresponding differences in mechanical behavior and in the observed microstructures. At high stresses and strain rates, specimens with as-machined surfaces were brittle at and below 1100 K when tested in air but showed fracture strains above 4% when deformed in argon. However, reproducible compressive ductility of 2–3% was attained on polished specimens tested in air. At intermediate stresses, the creep curves showed sudden and periodic increases in strain before the specimens failed catastrophically after about 80 h. Microstructural examination of these specimens revealed extensive oxidation within cracks. Constant load tests conducted at lower stresses below 100 MPa showed an apparent incubation period where the change in the length of the specimen was immeasurably small. Following the incubation period, which typically lasted between 10 and 110 h depending on stress, temperature, and surface condition, specimens increased significantly in length due to oxide growth. In this case, considerable oxide spalling occurred during the course of the test, often leading to a substantial decrease in the cross-sectional area of the specimen. Microstructural observations revealed extensive cracking in the oxide layer and in the matrix, where the cracks had originated at the oxide-metal interface. The effects of environment on the mechanical properties are rationalized with the help of a schematic environmental-deformation mechanism map.

Mechanical Properties of E21 Ti3AlC-base Alloy

2006 ◽  
Vol 980 ◽  
Author(s):  
Hideki Hosoda ◽  
Tomonari Inamura ◽  
Kenji Wakashima
Keyword(s):  
Mechanical Properties ◽  
Base Alloy ◽  
The Body ◽  
Nominal Composition ◽  
Second Phase ◽  
Positive Temperature ◽  
Compression Tests ◽  
Octahedral Interstitial Site ◽  
Temperature Range ◽  
Average Grain Size

AbstractMechanical properties and phase constitution of an E21-type Ti3AlC-base alloy were investigated by compression tests in a temperature range from room temperature (RT) to 1273K, scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The unit cell of E21 Ti3AlC is constructed by ¡§L12 Ti3Al¡¨ and a carbon atom occupying the body-center octahedral-interstitial-site surrounded by the Ti atoms. The nominal composition of the alloy was chosen to be the stoichiometric composition of 60mol%Ti-20mol%Al-20mol%C. The alloy was synthesized by mechanical alloying using high purity elemental powders followed by hot pressing at 1473K for 3hrs. It was found by XRD and SEM that the alloy was mainly composed of E21 Ti3AlC in addition to Cr2AlC-type Ti2AlC precipitates as a second phase. The density of Ti3AlC is calculated to be 4.29g/cm3 based on the lattice parameter of 0.4134nm of E21. The average grain size was 2μm by SEM. By the compression tests, the 0.2% flow stress at the temperature range from RT to 1073K exceeded 1GPa. The yield stress is comparably higher than those of other E21 intermetallic carbides: at 1073K, 1084MPa for Ti3AlC, 50MPa for Mn3AlC and 135MPa for Fe3AlC. Besides, a weak positive temperature dependence of strength was observed where the peak temperature was around 900K. This suggests that a Kear-Wilsdorf type dislocation pinning mechanism may be activated. It is concluded that E21 Ti3AlC-base alloy shows promise for a new high-temperature light-weight structural material.

In Situ Straining Experiments On Fe70AL30 Single Crystals

1994 ◽  
Vol 364 ◽  
Author(s):  
G. Molenat ◽  
H. Rösner ◽  
E. Nembach
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Single Crystals ◽  
Yield Stress ◽  
Transmission Electron Microscope ◽  
Intermetallic Alloys ◽  
Temperature Range ◽  
Transmission Electron

AbstractWith an aim to contributing to the understanding of the mechanical properties of Fe3Al-based intermetallic alloys, Fe-30 at. % Al single crystals have been strained in a transmission electron microscope below and in the temperature range of the yield stress anomaly (at 300K and 573K respectively).

Magnesium Alloy WE43 Produced by 3D Printing (SLM)

2020 ◽  
Vol 405 ◽  
pp. 345-350
Author(s):  
Patrícia Krištofová ◽  
Michaela Roudnicka ◽  
Jiří Kubásek ◽  
Alena Michalcová ◽  
Dalibor Vojtech ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Magnesium Alloy ◽  
3D Printing ◽  
Hardness Measurement ◽  
Compression Tests ◽  
Transmission Electron ◽  
Alloy We43 ◽  
Flexural Tests ◽  
Complex Parts

3D printing is a relatively new and quite attractive form of production, especially for complex parts. In this work, the SLM technology was used to prepare a magnesium alloy WE43 (Mg-4Y-3RE-Zr), a promising material for biodegradable implants. The aim of this study was to map the microstructure and mechanical properties of WE43 produced by SLM and compare it with conventional casting. Microstructure and chemical composition were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM). To examine mechanical properties, hardness measurement, compression tests and three-point flexural tests were carried out.

Processing and Mechanical Properties of Biphasic Calcium-Phosphate/Poly-L-Lactide Composite Biomaterials

2004 ◽  
Vol 471-472 ◽  
pp. 273-277
Author(s):  
Chak Yin Tang ◽  
N. Ignjatović ◽  
Dragan P. Uskokovic ◽  
P.S. Uskoković ◽  
K.C. Chan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Calcium Phosphate ◽  
Cortical Bone ◽  
Hot Pressing ◽  
Biphasic Calcium Phosphate ◽  
Wide Angle ◽  
Compression Tests ◽  
Temperature Range ◽  
Pressing Time

This study descripts processing of biphasic calcium-phosphate (BCP) and poly-L-lactide (PLLA) biocomposite implant material. The composite was obtained by mixing completely dissolved PLLA with granules of high crystalline BCP and was compacted by hot pressing using cylindrical dies at 450 K temperature and 98.1 MPa pressure, for 30 and 60 minutes. Wide-angle Xray structural (WAXS) analyses of BCP, PLLA and BCP/PLLA composite blocks were made followed by calorimetric (DSC) tests in the 320-520 K temperature range. Compression tests revealed that Young’s modulus and compressive strength of the composite increased with extended hot pressing time and were found to be within the bounds of the cortical bone values.

Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

1974 ◽  
Vol 32 ◽  
pp. 514-515
Author(s):  
S. Fujishiro
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Mechanical Processing ◽  
Ray Method ◽  
X Ray ◽  
Transmission Electron ◽  
Water Quench ◽  
Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

Dislocations in alumina deformed by prismatic slip

1978 ◽  
Vol 36 (1) ◽  
pp. 606-607
Author(s):  
J. Cadoz ◽  
J. Castaing ◽  
J. Philibert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basal Slip ◽  
Prismatic Slip ◽  
Compression Tests ◽  
Thin Sections ◽  
Burgers Vector ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

Study of dislocation loops in Arsenic-Rich as-grown GaAs

1987 ◽  
Vol 45 ◽  
pp. 350-351
Author(s):  
Byung-Teak Lee
Keyword(s):  
Point Defects ◽  
Electronic Devices ◽  
Arsenic Concentration ◽  
Stoichiometric Compound ◽  
Dislocation Loops ◽  
Gaas Crystal ◽  
Ion Milling ◽  
Transmission Electron ◽  
Arsenic Source ◽  
High Arsenic

Grown-in dislocations in GaAs have been a major obstacle in utilizing this material for the potential electronic devices. Although it has been proposed in many reports that supersaturation of point defects can generate dislocation loops in growing crystals and can be a main formation mechanism of grown-in dislocations, there are very few reports on either the observation or the structural analysis of the stoichiometry-generated loops. In this work, dislocation loops in an arsenic-rich GaAs crystal have been studied by transmission electron microscopy.The single crystal with high arsenic concentration was grown using the Horizontal Bridgman method. The arsenic source temperature during the crystal growth was about 630°C whereas 617±1°C is normally believed to be optimum one to grow a stoichiometric compound. Samples with various orientations were prepared either by chemical thinning or ion milling and examined in both a JEOL JEM 200CX and a Siemens Elmiskop 102.

A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

1992 ◽  
Vol 50 (2) ◽  
pp. 1024-1025
Author(s):  
Jun Liu ◽  
Katie E. Gunnison ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Ion Beam ◽  
Laminated Composite ◽  
Organic Matrix ◽  
Pearl Oyster ◽  
Interfacial Structure ◽  
Interfacial Region ◽  
Thin Sections ◽  
Organic Layers ◽  
Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

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