Improved constitutive description of single crystal viscoplastic deformation by dislocation climb

2012 ◽  
Vol 340 (4-5) ◽  
pp. 289-295 ◽  
Author(s):  
Ricardo A. Lebensohn ◽  
R.A. Holt ◽  
A. Caro ◽  
A. Alankar ◽  
C.N. Tomé
Keyword(s):  
Single Crystal ◽  
Dislocation Climb ◽  
Viscoplastic Deformation

TEM Analyses of Microstructure Evolution in Ex-Service Single Crystal CMSX-4 Gas Turbine Blade

2012 ◽  
Vol 186 ◽  
pp. 139-142 ◽  
Author(s):  
Beata Dubiel ◽  
Aleksandra Czyrska-Filemonowicz
Keyword(s):  
Single Crystal ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Microstructure Evolution ◽  
Dislocation Substructure ◽  
Dislocation Climb ◽  
Dislocation Slip ◽  
Gas Turbine Blade ◽  
Tem Analysis ◽  
Blade Height

TEM studies of the ex-service single crystal blade were performed to analyse the microstructural changes which control the degradation of the CMSX-4 superalloy during its exposure in a gas turbine. Microstructural analyses were focused mainly on evolution of the γ-γ’ morphology and examination of dislocation configurations in particular parts of the blade. Between the bottom and tip locations of the blade a pronounced differences in γ-γ’ morphology were observed. TEM analysis of the dislocation substructure showed that at the bottom of the blade the dislocation slip is mainly confined to the horizontal γ channels. Increasing of the temperature and decreasing of stress along the blade height resulted in the γ-γ’ rafting, formation of dislocation networks and intensification of the dislocation climb in vertical γ channels.

scholarly journals Cyclic viscoplastic deformation modeling of a nickel-based single crystal superalloy with [001] orientation

2018 ◽  
Vol 165 ◽  
pp. 19005 ◽  
Author(s):  
Rongqiao Wang ◽  
Bin Zhang ◽  
Dianyin Hu ◽  
Kanghe Jiang ◽  
Jianxing Mao ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Single Crystal ◽  
Deformation Behavior ◽  
Turbine Blades ◽  
Hysteresis Loops ◽  
Back Stress ◽  
Thermomechanical Fatigue ◽  
Growth Direction ◽  
Single Crystal Superalloy ◽  
Viscoplastic Deformation

Accurate simulations of cyclic viscoplastic deformation behaviors of single crystal superalloys which are widely used for the manufacture of gas turbine blades are important for the effective design and safety assessment in practice. In this context, based on the in-phase thermomechanical fatigue (IP TMF) and out-of-phase thermomechanical fatigue (OP TMF) experiments of the nickel-based single crystal superalloy with [001] orientation, a modified constitutive model has been developed to describe the deformation behavior under thermomechanical loadings. The TMF experiment results indicate that stable hysteresis loops with remarkable ratcheting appear in both IP TMF and OP TMF. And it’s worth noticing that the ratcheting growth direction of IP TMF and OP TMF are opposite. By introducing a Schmid stress rate related term to the back stress evolution equation, the slip-based Walker’s constitutive model is modified in this study. And the simulation results of the deformation behavior reveal good agreement with the experiments under different IP TMF and OP TMF conditions.

Dislocation Climb in the Electron Wind

1994 ◽  
Vol 338 ◽  
Author(s):  
Z. Suo
Keyword(s):  
Single Crystal ◽  
Thermodynamic System ◽  
Dislocation Climb ◽  
The Other ◽  
Equilibrium Thermodynamic ◽  
The Core ◽  
Vacancy Loops ◽  
Current Flows ◽  
Electron Wind ◽  
A Current

ABSTRACTWhen a current flows in a conductor, the electron wind causes atoms to diffuse. This paper considers the consequences of such diffusion along dislocation cores. A dislocation climbing in a crystal is viewed as a non-equilibrium thermodynamic system to define the force that drives selfdiffusion along the core. Not only is a dislocation a mass-transport pipe, it also climbs and generates more dislocations—all in the electron wind. A prismatic loop moves like a rigid disk, as atoms electro-migrate along the core from one edge of the loop to the other. Each loop is therefore a mass carrier responding to an electric current. Interstitial and vacancy loops can be simultaneously generated and subsequently climb in the opposite directions. The process transports mass in single crystal or bamboo-like interconnects at moderate temperatures.

{111} Planar Faults in a Quenced and Annealed NiAl-0.3Hf Single Crystal Alloy

1997 ◽  
Vol 3 (S2) ◽  
pp. 697-698
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
D. R. Hull
Keyword(s):  
Single Crystal ◽  
Mechanical Behavior ◽  
Significant Role ◽  
Defect Structure ◽  
Dislocation Climb ◽  
Stacking Fault ◽  
Alloying Elements ◽  
Dislocation Loops ◽  
Alloying Element ◽  
High Supersaturation

Quenched-in vacancies, vacancy agglomeration and solute-vacancy association can play a significant role in affecting the mechanical behavior of an alloy. It is well known that B2- NiAl can retain a high supersaturation of thermal vacancies which has been shown to manifest itself as dislocation loops, voids, or spiral dislocations. Dislocation climb loops formed in NiAl have been observed to emanate from impurity particles as concentric {100} loops which are prismatic in nature1. Impurity particles have also been shown to be responsible for nucleating faceted voids. However, addition of alloying elements can alter this mode of vacancy condensation and depending upon the degree of interaction between alloying element and vacancies, a completely different defect structure can result. In a recent study, addition of Boron to Fe-35 mol. % Al has been shown to produce complex {100} planar faults having both APB and stacking fault character, whereas Cr, Pd and W produced APBs on {111} planes.

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

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