Thermally activated deformation mechanisms in micro-alloyed two-phase titanium amminide alloys

1997 ◽  
Vol 233 (1-2) ◽  
pp. 1-14 ◽  
Author(s):  
F. Appel ◽  
U. Lorenz ◽  
M. Oehring ◽  
U. Sparka ◽  
R. Wagner
Keyword(s):  
Deformation Mechanisms ◽  
Two Phase ◽  
Thermally Activated

Mechanical Properties of Diverse High-Temperature Compounds–Thermal Variation of Microhardness and Crack Formation

1988 ◽  
Vol 133 ◽  
Author(s):  
Robert L. Fleischer
Keyword(s):  
Elastic Moduli ◽  
Crack Formation ◽  
The Other ◽  
Terminal Phase ◽  
Thermal Variation ◽  
Two Phase ◽  
Thermally Activated ◽  
High Melting Temperature ◽  
Binary Compounds ◽  
Single Crystal Plasticity

ABSTRACTMicrohardness vs temperature and elastic moduli have been measured for a suite of intermetallic compounds that melt above 1400°C. Binary intermetallics were selected to represent a variety of crystal structures and yet have optimal combinations of high melting temperature (Tm) and low specific gravity. Some deliberately two-phase alloys were prepared in which one phase is a terminal-phase metal and the other an intermetallic compound.Binary compounds can be described by two patterns. In those where plasticity is difficult, hardness decreased slowly with temperature up to Tm/2, the decrease being no more than that normally shown by the elastic moduli. In those compounds where single crystal plasticity is known (or at least plausible), microhardness decreases more rapidly than do elastic moduli, presumably due to thermally activated slip.

Molecular deformation mechanisms and mechanical properties of polymers simulated by molecular dynamics

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Ricardo Simões ◽  
António M. Cunha ◽  
Witold Brostow
Keyword(s):  
Molecular Dynamics ◽  
Mechanical Response ◽  
Polymeric Materials ◽  
Spatial Arrangement ◽  
Deformation Mechanisms ◽  
Second Phase ◽  
Two Phase ◽  
Chain Slippage ◽  
The Cost ◽  
Molecular Deformation

Abstract Virtual polymeric materials were created and used in computer simulations to study their behavior under uniaxial loads. Both single-phase materials of amorphous chains and two-phase polymer liquid crystals (PLCs) have been simulated using the molecular dynamics method. This analysis enables a better understanding of the molecular deformation mechanisms in these materials. It was confirmed that chain uncoiling and chain slippage occur concurrently in the materials studied following predominantly a mechanism dependent on the spatial arrangement of the chains (such as their orientation). The presence of entanglements between chains constrains the mechanical response of the material. The presence of a rigid second phase dispersed in the flexible amorphous matrix influences the mechanical behavior and properties. The role of this phase in reinforcement is dependent on its concentration and spatial distribution. However, this is achieved with the cost of increased material brittleness, as crack formation and propagation is favored. Results of our simulations are visualized in five animations.

Investigation of Multiferroic Properties of Spinel Ferrite (ZnFe2O4) and Ferroelectric (Na0.5Bi0.5TiO3) Composites

2019 ◽  
Vol 201 (1) ◽  
pp. 163-177
Author(s):  
Tanvi Bhasin ◽  
Ashish Agarwal ◽  
Sujata Sanghi ◽  
Manisha Yadav ◽  
Meenal ◽  
...  
Keyword(s):  
Spinel Ferrite ◽  
Xrd Analysis ◽  
Rietveld Analysis ◽  
Phase System ◽  
Reaction Route ◽  
Two Phase ◽  
Low Frequencies ◽  
Thermally Activated ◽  
Universal Power Law ◽  
Constant E

The composites of ZnFe2O4 and Na0.5Bi0.5TiO3 were synthesized by solid state reaction route. XRD analysis revealed the formation of two phase system successfully. Rietveld analysis of XRD data confirm that composites having cubic and rhombohedral corresponding to ferrite and ferroelectric phase respectively. The FESEM-EDX studies disclose that average grain sizes are ranges from 0.2 to 0.4 μm. The dielectric constant (ɛ’) and tanδ both shows dispersion at low frequencies and both increases with temperature due to increase in thermally activated hopping. Conductivity curves of each sample follow the universal power law. M–H plots suggest the paramagnetic behavior of these composites.

scholarly journals Quantitative analysis of microstructures produced by creep of Ti–48Al–2Cr–2Nb–1B: Thermal and athermal mechanisms

1998 ◽  
Vol 13 (3) ◽  
pp. 625-639 ◽  
Author(s):  
M. A. Morris ◽  
M. Leboeuf
Keyword(s):  
Tial Alloy ◽  
Mechanical Twinning ◽  
Deformation Mechanisms ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Pipe Diffusion ◽  
Thermally Activated ◽  
Fine Grain ◽  
Hardening Process ◽  
Secondary Stage

A γ-based TiAl alloy with equiaxed microstructure and fine grain size has been studied to analyze the deformation mechanisms responsible for the creep behavior. The microstructures produced by creep and high temperature deformation have been examined by TEM to obtain information about the different aspects characterizing the primary and secondary stages of creep. Mechanical twinning has been confirmed to occur in a fraction of the grains that never exceeds 50% while 1/2 ‹110› dislocations are active within all the γ grains. The twins are only responsible for a small amount of strain, but they lead to a subdivision of the microstructure and determine (directly or indirectly) the hardening process observed during the primary stage of creep. We have proposed that during the secondary stage the creep rate is determined by the unblocking of pinned dislocations by processes such as a pipe diffusion or cross slip that allow thermally activated glide of 1/2‹110› dislocations on (001) planes.

Phase Equilibria under Irradiation

1993 ◽  
Vol 311 ◽  
Author(s):  
P. Bellonw ◽  
F. Soisson ◽  
Y. Grandjean ◽  
G. Martin
Keyword(s):  
Phase Equilibria ◽  
Phase State ◽  
Equilibrium Phase ◽  
Atomic Diffusion ◽  
Equilibrium System ◽  
Stationary Probability Distribution ◽  
Average Composition ◽  
Two Phase ◽  
Thermally Activated ◽  
Far From Equilibrium

ABSTRACTA solid under irradiation is a far-from equilibrium system, and therefore phase equilibria in such a system cannot be assessed from equilibrium thermodynamics. Starting from a kinetic description which incorporates the various processes responsible for atomic diffusion (e.g. thermally activated jumps, replacement sequences or displacement cascades), the various possible steady-states can be identified analytically or numerically, as well as their kinetic evolution on varying the control parameters of the system (e.g. temperature, average composition, irradiation flux, cascade density …). Furthermore, from stochastic versions of the kinetic model, potentials governing the stationary probability distribution of states can be derived, allowing to build dynamical equilibrium phase diagrams.Illustrating the above approach on the A2-B2 order-disorder transition, we have identified irradiation-induced two-phase state, cascade size and density effects on phase stability. By incorporating point defects, such description is well suited to study irradiation-induced segregation at sinks in concentrated alloys.

Microstructures and mechanical properties of NiAl–Ni2AlHf alloys

1990 ◽  
Vol 5 (6) ◽  
pp. 1189-1196 ◽  
Author(s):  
M. Takeyama ◽  
C. T. Liu
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Volume Fraction ◽  
High Hardness ◽  
Lattice Misfit ◽  
Two Phase ◽  
Heusler Phase ◽  
Thermally Activated ◽  
Rapid Drop ◽  
Very High

The microstructure and mechanical properties of several Ni–Al–Hf alloys in the composition range between NiAl (β) and Ni2AlHf (Heusler phase) have been studied. The volume fraction of Heusler phase, Vf, in these alloys varies from about 15 to 96%. The lattice misfit between the β and Heusler phases in two-phase alloys is larger than 5%, indicating no coherency between them. The yield strength increases with increasing Vf at all temperatures to 1000°C. Compressive ductilities of 4 and 7% were obtained for the alloy with Vf of 15% at room temperature and 500°C, respectively, but they decreased to 0% with increasing Vf to 96%. The corresponding fracture mode is basically transgranular cleavage. However, all the alloys can be deformed extensively without fracture at 1000°C. The hardness of the Heusler alloy is very high (8.3 GPa) at room temperature, and it decreases gently with temperature to 600°C, followed by a rapid decrease to 1000°C. The brittleness and high hardness of the Ni2AlHf Heusler phase at low temperatures are interpreted in terms of internal lattice distortion resulting from its crystal structure. The thermally activated process of deformation takes place above 600°C, which is responsible for the rapid drop of the hardness of the alloys.

scholarly journals Superplastic Deformation Mechanisms of Alumina Zirconia Two Phase Ceramics

1999 ◽  
Vol 63 (7) ◽  
pp. 888-894 ◽  
Author(s):  
Koutarou Akashiro ◽  
Tsuneyuki Tanizawa ◽  
Satoru Ishihara ◽  
Norio Furushiro ◽  
Yukichi Umakoshi ◽  
...  
Keyword(s):  
Superplastic Deformation ◽  
Deformation Mechanisms ◽  
Two Phase

Detection of Hyperfine Precipitates in Nickel-Base Alloys

1968 ◽  
Vol 26 ◽  
pp. 438-439
Author(s):  
P. Beardmore
Keyword(s):  
Fine Particles ◽  
Dark Field ◽  
Deformation Mechanisms ◽  
Second Phase ◽  
Two Phase ◽  
Realistic Interpretation ◽  
Metal Foils ◽  
Fluorescent Screen ◽  
Dark Field Microscopy ◽  
Nickel Base

One of the primary objectives of the use of the electron microscope in the examination of metal foils is to ascertain the exact details of the microstructure in order that a realistic interpretation of the deformation mechanisms can be made. However, problems can arise in two phase structures in which the second phase is present as particles of widely differing size. In such cases it is possible to overlook the extremely fine particles because of the predominance of the larger particles on the fluorescent screen. Thus, fine details of the microstructure can remain undetected. This is particularly true in alloys in which both the precipitate and matrix have a common crystal structure and differ only in state of order. In such a structure, the detection and clarity of the precipitates is enhanced by dark field microscopy.

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