The Compression Creep Behavior of Ni3Al-X Single Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
Seiji Miura ◽  
Tohru Hayashi ◽  
Mitsuhiro Takekawa ◽  
Yoshinao Mishima ◽  
Tomoo Suzuki
Keyword(s):  
Activation Energy ◽  
Single Crystals ◽  
Power Law ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Constant Strain Rate ◽  
State Equation ◽  
Ternary Alloys ◽  
Plastic Behavior ◽  
Compression Tests

ABSTRACTCompressive creep behavior is investigated in ternary Ni3Al single crystals containing Ti, Si, Hf and Cr with stress axes parallel to the crystallographic orientation near [001]. Then a comparison is made with the results of high temperature compression tests under a constant strain rate for the same orientation where plastic behavior is characterized by a distinct yield drop followed by steadystate deformation. It is found that the deformation mechanism for the two cases is identical, namely octahedral viscous flow being expressed by the state equation of the power-law type with a stress exponent of about 3 to 4. The effect of offstoichiometry on the creep resistance is then examined in Ni3(Al,5 at%Ti) alloys with different Ni concentrations. The results support the observation in the polycrystalline compound where the creep resistance increases with Ni concentration on both sides of stoichiometry exhibiting a discontinuity at stoichiometry. Finally, the apparent activation energy in the power-law type state equation for the steady state creep deformation is estimated for all the ternary alloys examined. They are in general in good agreement with that for diffusion of ternary elements in Ni3Al. However, the relative magnitude of the value can not simply be compared since the activation energy depends on deviations from stoichiometry.

Effect of Off-Stoichiometry on the Creep Behavior of Binary and Ternary Ni3Al

1990 ◽  
Vol 213 ◽  
Author(s):  
Tohru Hayashi ◽  
Tetsumori Shinoda ◽  
Yoshinao Mishima ◽  
Tomoo Suzuki
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Power Law ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Equation ◽  
Ternary Element ◽  
Ternary Additions

ABSTRACTCompressive creep behavior is investigated In polycrystalline Ni3Al intermetallic compounds in which the focus is put on the effect of offstoichiometry and ternary additions of Ti, Ta, V and Co on the creep resistance of the compounds. In all cases, the steady-state creep rate has the power-law type dependence on the applied stress. The stress exponent thereby obtained leads us to regard the creep behavior of the compound to be of the Class I type. It is shown that the creep resistance Increases with increasing Ni concentration on both sides of the stoichiometric Ni3Al composition and a discontinuity exists in the variation at stoichiometry. The gap at the discontinuity becomes clearer by the addition of ternary element in most cases as compared to the binary Ni3Al. Although the exact reason for the phenomenon is not clearly understood at present, it is shown that it could be interpreted by the concentration dependence of activation energy in the power-law type creep equation.

scholarly journals Deformation of Ice Single Crystals Close to the Melting Point

1978 ◽  
Vol 21 (85) ◽  
pp. 445-455 ◽  
Author(s):  
Stephen J. Jones ◽  
Jean-Guy Brunet
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Single Crystals ◽  
Constant Strain Rate ◽  
Mean Value ◽  
Compression Tests ◽  
A Value ◽  
Polycrystalline Ice ◽  
Strain Rate Compression ◽  
Activation Energy Of Deformation

Abstract Constant strain-rate compression tests on ice single crystals at temperatures between –20°C and -0.2°C are described. The power-law dependence of yield stress on strain-rate gives a value of n which varies from 1.95±0.04 at –0.2°C to 2.07±0.08 at –20°C. The activation energy of deformation varies with strain-rate, but a mean value of 70±2 kJ mol–1 is obtained, with no indication of any increase close to maleting point,as has been found polycrystalline ice. An apparent work-hardening effect, at strains greater than 15%, is explained as being due to bending of the crystal changing the orientation of the basal planes.

scholarly journals Deformation of Ice Single Crystals Close to the Melting Point

1978 ◽  
Vol 21 (85) ◽  
pp. 445-455 ◽  
Author(s):  
Stephen J. Jones ◽  
Jean-Guy Brunet
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Single Crystals ◽  
Constant Strain Rate ◽  
Mean Value ◽  
Compression Tests ◽  
A Value ◽  
Polycrystalline Ice ◽  
Strain Rate Compression ◽  
Activation Energy Of Deformation

AbstractConstant strain-rate compression tests on ice single crystals at temperatures between –20°C and -0.2°C are described. The power-law dependence of yield stress on strain-rate gives a value of n which varies from 1.95±0.04 at –0.2°C to 2.07±0.08 at –20°C. The activation energy of deformation varies with strain-rate, but a mean value of 70±2 kJ mol–1 is obtained, with no indication of any increase close to maleting point,as has been found polycrystalline ice. An apparent work-hardening effect, at strains greater than 15%, is explained as being due to bending of the crystal changing the orientation of the basal planes.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

High Temperature Creep Behavior and Effects of Stacking Fault Energy in Mg-Y and Mg-Y-Zn Dilute Solid Solution Alloys

2014 ◽  
Vol 783-786 ◽  
pp. 491-496
Author(s):  
Mayumi Suzuki ◽  
Yasuyuki Murata ◽  
Kyosuke Yoshimi
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Creep Behavior ◽  
Ternary Alloys ◽  
Dislocation Creep ◽  
Prismatic Slip ◽  
Dislocation Slip ◽  
Self Diffusion ◽  
Controlling Mechanism ◽  
Hot Rolled

Compressive creep behavior of hot-rolled (40%) Mg-Y binary and Mg-Y-Zn ternary dilute solid solution alloys are investigated in this study. Creep strength is substantially improved by the addition of zinc. Activation Energy for creep in Mg-Y and Mg-Y-Zn alloys are around 200 kJ/mol at the temperature range from 480 to 570 K. These values are higher than the activation energy for self-diffusion coefficient in magnesium (135 kJ/mol). Many stacking faults, which are planar type defects are observed on the basal planes of the magnesium matrix in Mg-Y-Zn ternary alloys. TEM observation has been revealed that the non-basal a-dislocation slip is significantly activated by these alloys. The rate controlling mechanism of Mg-Y and Mg-Y-Zn dilute alloys are considered to the cross-slip or prismatic-slip controlled dislocation creep with high activation energy for creep, more than 1.5 times higher than the activation energy for creep controlled dislocation climb.

scholarly journals The orientation dependence of the strength of ice single crystals

2000 ◽  
Vol 46 (152) ◽  
pp. 41-44 ◽  
Author(s):  
Y. L. Trickett ◽  
I. Baker ◽  
P. M. S. Pradhan
Keyword(s):  
Strain Rate ◽  
Single Crystals ◽  
Axial Strain ◽  
Constant Strain Rate ◽  
Peak Stress ◽  
Deformation Mode ◽  
Orientation Dependence ◽  
Compression Tests ◽  
Ice Flow ◽  
Critical Resolved Shear Stress

AbstractSingle crystals with a wide variety of orientations were cut from large pucks of laboratory-grown ice. Constant-strain-rate compression tests were performed on the crystals either at an axial strain rate of 1 × 10−5 s−1at –20°C or at axial strain rates from 1 × 10−6 s−1 to 1 × 10−4 s−1 at –10°C. In agreement with previous studies of ice flow, the compression tests showed a linearly rising stress with increasing strain, followed by a sharply declining stress after reaching a peak. With further strain, the sharp decline in stress slowed and the flow stress approached a plateau that was only weakly dependent on strain. For all crystallographic orientations, it was found that Schmid’s (critical resolved shear stress) law was obeyed by the peak stress. Slip lines clearly showed that basal slip was the deformation mode.

The Creep Behavior of Cr Modified Ni3 Al Single Crystals

1988 ◽  
Vol 133 ◽  
Author(s):  
S. E. Hsu ◽  
C. H. Tong ◽  
T. S. Lee ◽  
T. S. Liu
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Single Crystals ◽  
Creep Behavior ◽  
Aluminum Content ◽  
Dislocation Core ◽  
Transient Creep ◽  
Cr Addition ◽  
Dislocation Core Structure ◽  
Different Levels

ABSTRACTNi-Al-Cr single crystals with 4 at% Cr and different levels of aluminum content are grown in a directional solidification facility. The crystals are creep tested at temperatures from 760°C to 860°C. Steady state, as well as transient, creep rates are measured. The results show that Cr modified Ni3 A1, when tested along the <100> direction, exhibit remarkably high values of activation energy for creep. Along with evidence from dislocation structures, it is likely that there is a change in the dislocation core structure upon Cr addition.

Effects of Stacking Faults on High Temperature Creep Behavior in Mg-Y-Zn Based Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1602-1607 ◽  
Author(s):  
Mayumi Suzuki ◽  
Kouichi Maruyama
Keyword(s):  
Activation Energy ◽  
Creep Behavior ◽  
Stacking Faults ◽  
Dislocation Motion ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Ternary Alloys ◽  
Solute Content ◽  
Planar Defects ◽  
Multiple Addition

Compressive creep behavior of hot-rolled (40%) Mg-Y and Mg-Y-Zn alloys are investigated at 480 ~ 650 K. Creep strength is substantially improved by the simultaneous addition of yttrium and zinc. The minimum creep rate of Mg-0.9mol%Y-0.04mol%Zn (WZ301) alloy decreases to 1/10 lower than that of Mg-1.1mol%Y (W4) alloy at 650 K. Activation energy for creep in W4 and WZ301 alloys are more than 200 kJ/mol at the temperature range of 480 ~ 550 K. These values are higher than the activation energy for self-diffusion coefficient in magnesium (135 kJ/mol). Many stacking faults (planar defects, PDs) are only observed on the basal planes of the matrix in Mg-Y-Zn ternary alloys. Stacking fault energy is considered to decrease by the multiple-addition of yttrium and zinc. The size and density of these planar defects depend on solute content, aging condition. TEM observation has been revealed that the decreasing of the stacking fault energy affects the distribution of dislocations during creep. Many a-dislocations on basal planes are extended significantly. Dislocation motion is restricted significantly by both of these two types of stacking faults (planar type and extended dislocations).

scholarly journals The effects of sulfuric acid on the mechanical properties of ice single crystals

2000 ◽  
Vol 46 (153) ◽  
pp. 239-243 ◽  
Author(s):  
Y. L. Trickett ◽  
I. Baker ◽  
P. M. S. Pradhan
Keyword(s):  
Sulfuric Acid ◽  
Strain Rate ◽  
Single Crystals ◽  
Axial Strain ◽  
Constant Strain Rate ◽  
Peak Stress ◽  
Solubility Limit ◽  
Compression Tests ◽  
Preliminary Examination ◽  
First Time

AbstractIce single crystals of various orientations containing various concentrations of H2SO4 up to 11.5 ppm were cut from large pucks of laboratory-grown ice. Constant-strain-rate compression tests were performed on the doped ice crystals both at −20°C at an axial strain rate of 1 × 10−5 s−1 and at −10°C at 1 × 106 s−1. The stress–strain curves showed a linearly rising stress with increasing strain, followed by a sharply declining stress after reaching a peak. With further strain, the sharp decline in stress slowed. The tests clearly showed, for the first time, that this naturally occurring impurity dramatically decreases both the peak stress and the subsequent flow stress of ice single crystals. The decrease in the peak strength was related to the square root of the concentration of H2SO4 up to 11.5 ppm, suggesting that the solubility limit of H2SO4 in ice is at least 11.5 ppm. The sulfuric acid also appeared to increase the ductility of the ice. Preliminary examination of a doped ice single crystal by synchrotron X-ray topography suggested that sulfuric acid dramatically increases the grown-in dislocation density.

COMPRESSION CREEP BEHAVIOR OF B2 AL-NI-RU TERNARY ALLOYS

2006 ◽  
Vol 980 ◽  
Author(s):  
Fang Cao ◽  
Tresa M. Pollock
Keyword(s):  
Creep Behavior ◽  
Phase Field ◽  
Creep Resistance ◽  
Ternary Alloys ◽  
Continuous Increase ◽  
Screw Dislocations ◽  
Compression Creep ◽  
Transient Experiments ◽  
B2 Phase ◽  
Edge Dislocations

AbstractThe compression creep behavior of five Al- Ni-Ru ternary alloys with compositions across the NiAl-RuAl B2 phase field has been investigated within the temperature range of 950 °C to 1050 °C. A continuous increase of the melting temperature and creep resistance with increasing Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Al-deficient alloys. Conversely, jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. Dislocation substructures and transient experiments suggest a transition of the creep mechanism from viscous glide controlled to jogged screw motion in these alloys.

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