Apparent Activation Energy for High-Temperature Deformation of EN AW 2014

2009 ◽  
Vol 28 (5) ◽  
pp. 315-322 ◽  
Author(s):  
Jana Bidulská, ◽  
Imrich Pokorný, ◽  
Tibor Kvačkaj, ◽  
Róbert Bidulský, ◽  
Marco Actis Grande,
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Deformation ◽  
Temperature Deformation

Hot Working of the ZEK200 Magnesium Alloy

2008 ◽  
Vol 604-605 ◽  
pp. 212-222 ◽  
Author(s):  
S. Spigarelli ◽  
Mohamad El Mehtedi ◽  
P. Ricci
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Direct Chill ◽  
Equivalent Strain ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Torsion Testing ◽  
A Value ◽  
Complete Recrystallization

The high temperature workability of the ZEK200 Mg-alloy produced by Direct Chill casting (DC) was investigated by torsion testing between 200 and 450°C. The alloy exhibited a higher strength and a slightly lower equivalent strain to fracture than AZ31 and ZM21 produced by DC. The calculation of the constitutive equation gave a value of the activation energy for high temperature deformation close to 175 kJ/mol, in line with those calculated by following the same procedure in AZ31 and ZM21. Partial or complete recrystallization of the deformed structure was observed at 350 and 400°C respectively. Grain growth occurred after recrystallization in the samples tested at 450°C.

Comparison of the High-Temperature Deformation of Alumina-Zirconia and Alumina-Zirconia-Mullite Composites

2005 ◽  
Vol 20 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Tiandan Chen ◽  
Martha L. Mecartney
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Strain Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Reactive Processing ◽  
Lower Activation ◽  
Lower Activation Energy

An alumina-based ceramic codispersed with 15 vol% zirconia and 15 vol% mullite (AZM) was synthesized by reactive processing, and the creep behavior was compared to alumina with 30 vol% zirconia (AZ). Constant stress compressive creep behavior for AZM exhibited a stress exponent of 2 and an activation energy of 770 KJ/mol, while a similar stress exponent but lower activation energy of 660 KJ/mol was found for AZ. The strain rate of AZM, however, was more than twice that of the AZ under the same deformation conditions, indicating a better potential for superplastic shape forming.

High Temperature Deformation Behavior and Processing Maps of AZ31 Alloy Deformed in Tension versus Compression

2019 ◽  
Vol 794 ◽  
pp. 305-314
Author(s):  
Kamineni Pitcheswara Rao ◽  
Kalidass Suresh ◽  
Yellapregada Venkata Rama Krishna Prasad
Keyword(s):  
Activation Energy ◽  
Dynamic Recrystallization ◽  
Apparent Activation Energy ◽  
Az31 Alloy ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Processing Maps ◽  
State Of Stress ◽  
Flow Stress Data

The effect of the applied state-of-stress on the processing maps depicting the mechanisms for hot working of hot extruded Mg-3Al-1Zn alloy has been evaluated. Flow stresses at various temperatures in the range 300 – 500 °C and strain rates in the range 0.0003 – 1 s-1 have been measured by deforming in compression and in tension. Processing maps have been developed from the respective flow stress data at a strain of 0.1. The maps are essentially similar irrespective of the mode of deformation – compression or tension, and exhibited two domains in the temperature and strain rate ranges: (1) 375 – 500 °C and 0.0003 – 0.01 s-1, and (2) 450 – 500 °C and 0.1 – 1 s-1. On the basis of slower strain rates, high tensile ductility, and the apparent activation energy (152 kJ/mole closer to that for self-diffusion), Domain #1 is interpreted in terms of the occurrence of climb controlled dynamic recrystallization. In Domain #2, which occurs at higher strain rates and has an apparent activation energy near to 165 kJ/mole, dynamic recrystallization occurs that involves second order pyramidal slip {11-22} <11-2-3> and recovery by cross-slip of screw dislocations. The state-of-stress imposed on the specimen (compression or tension) does not have any significant effect on the processing maps or the kinetics of hot deformation.

High-Temperature Deformation of Yba2Cu307-8 With Ag Additions

1989 ◽  
Vol 169 ◽  
Author(s):  
J.L. Routbort ◽  
K.C. Goretta ◽  
J.P. Singh
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Temperature ◽  
Flow Stress ◽  
Compressive Strain ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Steady State Flow ◽  
Ag Additions

AbstractThe steady‐state flow stress of YBa2Cu3O7‐δ containing 15 to 30 vol.% Ag has been measured in air at nearly constant compressive strain rates between 5 x 10‐6 and 1 x 10‐4 s‐1 from 830 to 900°C. Addition of Ag dramatically decreases the flow stress compared to that of the pure superconductor, but the stress exponents and the activation energy for deformation remain unchanged.

Effect of Heat Treatment Conditions on the High Temperature Deformation of 6082-Al Alloy

2009 ◽  
Vol 83-86 ◽  
pp. 407-414 ◽  
Author(s):  
Mahmoud S. Soliman ◽  
Ehab El-Danaf ◽  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Threshold Stress ◽  
High Temperature Deformation ◽  
Single Type ◽  
Temperature Deformation ◽  
Al Alloy ◽  
Second Phase ◽  
Dislocation Interaction ◽  
6082 Al Alloy

High-temperature deformation of an artificially aged 6082-Al alloy was conducted in the present investigation. Tensile tests were carried out at temperatures of 623, 673 and 723 K at various strain rates ranging from 5x10-5 to 2x10-2 s-1. The behavior of the alloy is characterized by high stress exponent, n and high apparent activation energy, Qa that are higher than what is usually observed in Al and Al solid-solution alloys under similar experimental conditions, which implies the presence of threshold stress; this behavior results from dislocation interaction with second phase particles. The threshold stress, σo values were seen to decrease exponentially with temperature. By incorporating the threshold stress in the analysis, the true activation energy, Qt was calculated to be close to that of dislocation pipe diffusion in Al. Analysis of the experimental data of the alloy in terms of the Zener- Hollomon parameter vs. normalized effective stress, revealed a single type of deformation behavior with an n value of ~7. Measurements showed that the values of elongation percent at failure increase with strain rate and temperature.

Superplasticity-Like Behavior, Microstructures and Deformation Mechanism Map in Superlight Mg-6Li-3Zn Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 2504-2510
Author(s):  
Fu Rong Cao ◽  
Ren Guo Guan ◽  
Hua Ding ◽  
Ying Long Li ◽  
Ge Zhou ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Initial Strain Rate ◽  
Lattice Diffusion ◽  
Initial Strain ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Diffusion Activation Energy

Mg-6Li-3Zn alloy sheets were prepared by melting and casting, and heavy rolling with a total reduction of 94%. The high-temperature mechanical behavior, microstructures and deformation mechanisms were investigated. The maximum elongation to failure of 300% was demonstrated at 623K and an initial strain rate of 1.67×10-3s-1. Observations by optical microscope, transmission electron microscope reveal that significant dynamic recrystallization and grain refinement occurred in banded grains at 573K and an initial strain rate of 1.67×10-3s-1, under which the subgrain contour was ambiguous and dislocation distribution was relatively uniform. It is shown by newly constructed deformation mechanism map that the high-temperature deformation mechanism in Mg-6Li-3Zn alloy sheet with banded grains at 573K and an initial strain rate of 1.67×10-3 s-1 is dislocation viscous glide controlled by lattice diffusion, the stress exponent is 3 (strain rate sensitivity exponent 0.33) and deformation activation energy is 134.8 kJ mol-1, which is the same as the lattice diffusion activation energy of magnesium.

The Deformability of Fe-Ni Superalloy during High Temperature Deformation

2016 ◽  
Vol 246 ◽  
pp. 221-224
Author(s):  
Kazimierz J. Ducki ◽  
Kinga Rodak ◽  
Lilianna Wojtynek
Keyword(s):  
Activation Energy ◽  
Plastic Deformation ◽  
High Temperature ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Flow Curves ◽  
Plastic Properties ◽  
Hot Torsion ◽  
Total Fracture

The influence of initial soaking and parameters of plastic deformation on the deformability of A-286 superalloy have been presented. The hot-torsion tests were executed at constant strain rates of 0.1 and 1.0 s-1, at testing temperatures in the range 900-1150°C and were conducted until total fracture of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of flow stresses and strain limits. Activation energy for hot working Q was assessed for the alloy after two variants of previous heating, i.e. 1100°C/2 h and 1150°C/2 h.

High Temperature Deformation of Wrought Zn-Containing Magnesium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1482-1487 ◽  
Author(s):  
S. Spigarelli ◽  
Mohamad El Mehtedi ◽  
D. Ciccarelli ◽  
Menachem Bamberger ◽  
Giuseppe Cupitò ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Flow Stress ◽  
Magnesium Alloys ◽  
Temperature Response ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Lower Strength ◽  
The Difference ◽  
Zn Alloys

The high temperature response in torsion and creep of two extruded Mg-Zn alloys was investigated in the present study. The alloy 0 (Mg-2Zn-1Mn) was found to exhibit a lower strength than the alloy 2 (Mg-0.55Zn-0.79Mn-0.75Al-0.17Ca), even if the activation energy for creep was similar for both materials (170-180 kJ/mol). The difference in flow stress was here preliminarily attributed to the precipitation of fine Al2Ca particles.

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