High-temperature deformation-induced defects and Burgers vector determination of dislocations in the Al70Co15Ni15 decagonal quasicrystal

AbstractWe attempted to calculate the breakaway stress σb of dislocation from attractive junction made by reaction of dislocations. Assuming that the force f acting on the unit length of dislocation with the Burgers vector B under a shear stress τa is f τ∣b˝∣ where b˝ is the phonon component of B, and that the elastic energy per unit length of dislocation W is approximated by W = G(∣b˝∣2 + c2 ∣b˔∣2) where G is the shear modulus, b˔ the phason component of B and c2 a coefficient of about 3.1 × 10−3. Using the values G = 48.4 GPa at 1070 K, the Taylor factor M = 3 and the measured dislocation density of 1.8 × 1013 m−2, we calculated σb for 21 possible dislocation reactions. Picking up the most possible dislocation reactions, σb distributed between 50 and 80 MPa, and the average of them was 64 MPa. This result strongly suggested the possibility that the main part of the internal stress of the high-temperature deformation of icosahedral Al-Pd-Mn is explained by σb.

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High-temperature plasticity of cubic bismuth oxide

Journal of Materials Research ◽

10.1557/jmr.1996.0180 ◽

1996 ◽

Vol 11 (6) ◽

pp. 1433-1439 ◽

Cited By ~ 5

Author(s):

Anne Vilette ◽

S. L. Kampe

Keyword(s):

High Temperature ◽

Strain Rate ◽

Bismuth Oxide ◽

Rate Sensitivity ◽

High Temperature Deformation ◽

Temperature Deformation ◽

Cubic Phase ◽

Superplastic Behavior ◽

Wide Range

Cubic (δ) bismuth oxide (Bi2O3) has been subjected to high temperature deformation over a wide range of temperatures and strain rates. Results indicate that bismuth oxide is essentially incapable of plastic deformation at temperatures below the monoclithic to cubic phase transformation which occurs at approximately 730 °C. Above the transformation temperature, however, Bi2O3 is extensively deformable. The variability of flow stress to temperature and strain rate has been quantified through the determination of phenomenological-based constitutive equations to describe its behavior at these high temperatures. Analysis of the so-determined deformation constants indicate an extremely strong sensitivity to strain rate and temperature, with values of the strain-rate sensitivity approaching values commonly cited as indicative of superplastic behavior.

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Modelling Dynamic Recovery and Recrystallization of Metals by a New Non-Equilibrium Thermodynamics Approach

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.517 ◽

2007 ◽

Vol 558-559 ◽

pp. 517-522

Author(s):

Ming Xin Huang ◽

Pedro E.J. Rivera-Díaz-del-Castillo ◽

Sybrand van der Zwaag

Keyword(s):

Steady State ◽

High Temperature ◽

Flow Stress ◽

Dislocation Density ◽

Dynamic Recovery ◽

High Temperature Deformation ◽

Temperature Deformation ◽

Equilibrium Thermodynamics ◽

Burgers Vector ◽

Non Equilibrium

A non-equilibrium thermodynamics-based approach is proposed to predict the dislocation density and flow stress at the steady state of high temperature deformation. For a material undergoing dynamic recovery and recrystallization, it is found that the total dislocation density can be expressed as ( )2 ρ = λε& b , where ε& is the strain rate, b is the magnitude of the Burgers vector and λ is a dynamic recovery and recrystallization related parameter.

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