Creep of Anomalous Ni3Ga

1996 ◽  
Vol 460 ◽  
Author(s):  
M J Lunt ◽  
Y Q Sun
Keyword(s):  
Yield Stress ◽  
Creep Strength ◽  
Rapid Decrease ◽  
Steady State Creep ◽  
Intermetallic Alloys ◽  
Creep Tests ◽  
Screw Dislocations ◽  
Cube Plane ◽  
Ordered Intermetallic ◽  
Inverse Creep

ABSTRACTNi3Ga is among a number of LI2 ordered intermetallic alloys whose yield stress increases with temperature. In this work we have examined the creep strength of [123] and [001] oriented Ni3Ga specimens in the temperature regime of the yield stress anomaly and confirmed that the creep strength shows the normal rapid decrease with temperature. Inverse creep occurs in the [001] specimens where slip is on the {111} planes only. [123] specimens exhibit steady-state creep and slip line and TEM observations have shown slip on the cube plane and dislocations of both <110> and <100> Burgers vectors are present. We have carried out creep tests of prestrained [123] samples and demonstrated that the storage of primary <110> {111} screw dislocations, locked in the Kear-Wilsdorf configuration, has no effect on creep.

New Description of Steady-State Creep Rate, Yield Stress, Stress Relaxation and Their Interrelation

2005 ◽  
Vol 482 ◽  
pp. 319-322
Author(s):  
Jan Kohout
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Creep Rate ◽  
Yield Stress ◽  
Applied Stress ◽  
Stress Sensitivity ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Tests ◽  
Sensitivity Parameter

The steady-state creep rate increases with temperature according to the Arrhenius equation and its increase with applied stress is mostly described by the power law. Combining both these laws, equation ) exp( RT Qa n − µ s e& is obtained, where apparent activation energy a Q and stress sensitivity parameter n are considered to be constants. But most measurements show some dependence of activation energy on applied stress and of stress sensitivity parameter on temperature. An equation respecting these facts is derived in the paper and verified using some published results of creep tests. Based on this derived equation, the dependence of yield stress on temperature and strain rate and an equation describing the relaxation curves are deduced.

What Controls Temperature Dependence of Yield Stress in L12-Ordered Intermetallic Compounds?

2015 ◽  
Vol 1760 ◽  
Author(s):  
Haruyuki Inui ◽  
Norihiko L. Okamoto
Keyword(s):  
Temperature Dependence ◽  
Yield Stress ◽  
Intermetallic Compounds ◽  
Low Temperatures ◽  
Rapid Decrease ◽  
Partial Dislocations ◽  
Ordered Intermetallic ◽  
Image Position ◽  
Made In

ABSTRACTThe temperature dependence of yield stress and the associated dislocation dissociation in L12 intermetallic compounds are investigated in order to check the feasibility of the classification of L12 intermetallic compounds so far made in terms of the planarity of core structures of partial dislocations with b = 1/2<110> and 1/3<112> on {111} and {001} glide planes. In contrast to what is believed from the classification, the motion of APB-coupled dislocations is evidenced to give rise to the rapid decrease in yield stress at low temperatures for Pt3Al. In view of the fact that rapid decrease in yield stress at low temperatures is also observed in Co3(Al,W) and Co3Ti in which APB-coupled dislocations are responsible for deformation, the SISF-type dissociation is not a prerequisite for the rapidly decreasing CRSS for slip on (111) and the relative magnitudes of the APB energy on (111) and the SISF energy on (111) cannot be a primary factor that determines the type of the temperature dependence of CRSS for L12 compounds. The importance of the CSF energy as a factor determining the type of the temperature dependence of yield stress for L12 compounds through the changes in the planarity of the core structure of the APB-coupled partial dislocation with bp = ½[1$\overline 1$0] is discussed in the light of experimental evidence obtained from Pt3Al.

Slip Systems in Ni3(Al, Ti) At Temperatures Above the Peak in Flow Stress

1988 ◽  
Vol 133 ◽  
Author(s):  
Y. Q. Sun ◽  
P. M. Hazzledine
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Deformation Behaviour ◽  
Slip Systems ◽  
Intermetallic Alloys ◽  
Weak Beam ◽  
Cube Plane ◽  
Ordered Intermetallic ◽  
Beam Technique

ABSTRACTDislocations in single crystals of Ni3(Al, Ti) deformed at temperatures above the peak in flow stress have been studied by the TEM “weak-beam” technique. <110> dislocations on the primary cube plane are mostly of edge character, and they have been observed to transform into “super” Lomer- Cottrell locks. <100> dislocations, by contrast, are principally of 45° character. They are believed also to become immobilized by dissociation on {111} planes. Properties of both dislocations on cube planes are discussed and are related to the deformation behaviour of L12ordered intermetallic alloys.

Bonding and stability in the ordered alloys FeV and CoTi. Comparison with FeTi

1985 ◽  
Vol 50 (10) ◽  
pp. 2093-2100
Author(s):  
Štěpán Pick ◽  
Mojmír Tomášek ◽  
Mojmír Šob
Keyword(s):  
Phase Diagrams ◽  
Partial Wave ◽  
Partial Wave Analysis ◽  
Intermetallic Alloys ◽  
Wave Analysis ◽  
Ordered Alloys ◽  
Ordered Intermetallic ◽  
Cscl Structure ◽  
Ionic Effects

Partial wave analysis together with the qualitative examination of hybridization has been performed for two ordered intermetallic alloys with CsCl structure, FeV, and CoTi. The results resemble those obtained previously for FeTi, although important deviations are present as well. The stabilization of the ordered phase is again due to ionic effects. Qualitative arguments are suggested to explain the small stability of the CsCl phase of FeV and some differences in the FeTi and CoTi phase diagrams.

scholarly journals Influence of Different Annealing Atmospheres on the Mechanical Properties of Freestanding MCrAlY Bond Coats Investigated by Micro-Tensile Creep Tests

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 692 ◽  
Author(s):  
Sven Giese ◽  
Steffen Neumeier ◽  
Jan Bergholz ◽  
Dmitry Naumenko ◽  
Willem J. Quadakkers ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Creep Strength ◽  
Bond Coat ◽  
Oxide Dispersion Strengthened ◽  
Tensile Creep ◽  
Creep Tests ◽  
Bond Coats ◽  
Nial Phase ◽  
Lower Strain ◽  
Plasma Sprayed

The mechanical properties of low-pressure plasma sprayed (LPPS) MCrAlY (M = Ni, Co) bond coats, Amdry 386, Amdry 9954 and oxide dispersion strengthened (ODS) Amdry 9954 (named Amdry 9954 + ODS) were investigated after annealing in three atmospheres: Ar–O2, Ar–H2O, and Ar–H2–H2O. Freestanding bond coats were investigated to avoid any influence from the substrate. Miniaturized cylindrical tensile specimens were produced by a special grinding process and then tested in a thermomechanical analyzer (TMA) within a temperature range of 900–950 °C. Grain size and phase fraction of all bond coats were investigated by EBSD before testing and no difference in microstructure was revealed due to annealing in various atmospheres. The influence of annealing in different atmospheres on the creep strength was not very pronounced for the Co-based bond coats Amdry 9954 and Amdry 9954 + ODS in the tested conditions. The ODS bond coats revealed significantly higher creep strength but a lower strain to failure than the ODS-free Amdry 9954. The Ni-based bond coat Amdry 386 showed higher creep strength than Amdry 9954 due to the higher fraction of the β-NiAl phase. Additionally, its creep properties at 900 °C were much more affected by annealing in different atmospheres. The bond coat Amdry 386 annealed in an Ar–H2O atmosphere showed a significantly lower creep rate than the bond coat annealed in Ar–O2 and Ar–H2–H2O atmospheres.

Effect of multi-pass friction stir processing on thermal distribution and mechanical properties of AZ91

2020 ◽  
Vol 21 (4) ◽  
pp. 411
Author(s):  
Hoda Agha Amini Fashami ◽  
Nasrollah Bani Mostafa Arab ◽  
Mohammad Hoseinpour Gollo ◽  
Bahram Nami
Keyword(s):  
Mechanical Properties ◽  
Creep Strength ◽  
Friction Stir Processing ◽  
Material Behavior ◽  
Az91 Alloy ◽  
Residual Stress Field ◽  
Three Dimensional Model ◽  
Creep Tests ◽  
Friction Stir ◽  
Thermal Distribution

In this paper, the effect of multi-pass friction stir processing on mechanical properties of AZ91 alloy has been studied. For this purpose, the microhardness, tensile, and creep tests were conducted at several temperatures. Optical microscopy and scanning electron micrograph were used to study the microstructure of the processed samples. The experimental results indicated that at room temperature, the microhardness, tensile, and creep strength of the processed samples as compared to the unprocessed ones increased by 23%, 29%, and 38%, respectively. Also, after friction stir processing, the tensile and creep strength of the samples at 210 °C increased by 31% and 47%. In addition, a three-dimensional model was developed to simulate two-pass friction stir processing using ABAQUS/Explicit software. This model involved the Johnson-Cook models for defining material behavior during the process and identifying the fracture criterion. To control the mesh distortion during consecutive passes, the Arbitrary Lagrangian-Eulerian technique was used. Using the developed model, the peak temperature, thermal distribution, and residual stress field during multi-pass friction stir processing on AZ91 have been studied. The empirical results indicated the beneficial influence of the multi-pass friction stir processing on the microstructure and high-temperature mechanical properties of AZ91 alloy.

Ordered intermetallic alloys, part I: Nickel and iron aluminides

JOM ◽  
1993 ◽  
Vol 45 (5) ◽  
pp. 38-44 ◽  
Author(s):  
C. T. Liu ◽  
K. S. Kumar
Keyword(s):  
Iron Aluminides ◽  
Intermetallic Alloys ◽  
Ordered Intermetallic

Effect of Ausforming on Creep Strength of G91 Heat-Resistant Steel

2018 ◽  
Vol 941 ◽  
pp. 400-406 ◽  
Author(s):  
Javier Vivas ◽  
Rosalia Rementeria ◽  
Marta Serrano ◽  
Eberhard Altstadt ◽  
David San Martín ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Creep Strength ◽  
Operating Temperature ◽  
Strengthening Mechanism ◽  
Processing Route ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Conventional Heat Treatment

The major challenge in a heat-resistant steel is to generate thermally stable microstructures that allow increasing the operating temperature, which will improve the thermal efficiency of the power plant without diminishing strength or time to rupture. The strengthening mechanism in tempered martensitic 9Cr steels comes mainly from the combination of solid solution effect and of precipitation hardening by fine MX carbo-nitrides, which enhance the sub-boundary hardening. This work is focused on the effect of ausforming processing on MX nanoprecipitation, on both their distribution and number density, during the subsequent tempering heat treatment. The creep strength at 700 oC was evaluated by small punch creep tests. The creep results after ausforming were compared to those obtained after conventional heat treatment concluding, in general, that ausforming boosts the creep strength of the steel at 700 oC. Therefore, conventional ausforming thermomechanical treatment is a promising processing route to raise the operating temperature of 9Cr heat-resistant steels.

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