scholarly journals How Nanoscale Dislocation Reactions Govern Low- Temperature and High-Stress Creep of Ni-Base Single Crystal Superalloys

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 134 ◽  
Author(s):  
David Bürger ◽  
Antonin Dlouhý ◽  
Kyosuke Yoshimi ◽  
Gunther Eggeler
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
High Stress ◽  
Shear Stresses ◽  
Creep Tests ◽  
Shear Creep ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Crystallographic Shear ◽  
Shear System

The present work investigates γ-channel dislocation reactions, which govern low-temperature (T = 750 °C) and high-stress (resolved shear stress: 300 MPa) creep of Ni-base single crystal superalloys (SX). It is well known that two dislocation families with different b-vectors are required to form planar faults, which can shear the ordered γ’-phase. However, so far, no direct mechanical and microstructural evidence has been presented which clearly proves the importance of these reactions. In the mechanical part of the present work, we perform shear creep tests and we compare the deformation behavior of two macroscopic crystallographic shear systems [ 01 1 ¯ ] ( 111 ) and [ 11 2 ¯ ] ( 111 ) . These two shear systems share the same glide plane but differ in loading direction. The [ 11 2 ¯ ] ( 111 ) shear system, where the two dislocation families required to form a planar fault ribbon experience the same resolved shear stresses, deforms significantly faster than the [ 01 1 ¯ ] ( 111 ) shear system, where only one of the two required dislocation families is strongly promoted. Diffraction contrast transmission electron microscopy (TEM) analysis identifies the dislocation reactions, which rationalize this macroscopic behavior.

Constitutive Model for Anisotropic Creep Behaviors of Single-Crystal Ni-Base Superalloys in the Low-Temperature, High-Stress Regime

2012 ◽  
Vol 43 (6) ◽  
pp. 1861-1869 ◽  
Author(s):  
Yoon Suk Choi ◽  
Triplicane A. Parthasarathy ◽  
Christopher Woodward ◽  
Dennis M. Dimiduk ◽  
Michael D. Uchic
Keyword(s):  
Low Temperature ◽  
Constitutive Model ◽  
Single Crystal ◽  
High Stress ◽  
Stress Regime ◽  
Anisotropic Creep

An Empirical Constitutive Correlation for Regular Jugged Discontinuity of Rock Surfaces

2013 ◽  
Vol 5 (2) ◽  
pp. 258-268 ◽  
Author(s):  
Bin Yang ◽  
Sihao Mo ◽  
Ping Wu ◽  
Chaoqing He
Keyword(s):  
Deformation Property ◽  
Creep Property ◽  
Shear Stresses ◽  
Test Results ◽  
Creep Tests ◽  
Shear Creep ◽  
Burger Model ◽  
Structural Plane ◽  
Creep Velocity

AbstractThis paper presents a physical investigation and mathematical analysis on mechanical behavior of the regular jugged discontinuity. In particular, we focus on the creep property of structural plane with various slope angles under different normal stress through shear creep tests of structural plane under shear stresses. According to the test results, the shear creep property of structural plane was described and the creep velocity and long-term strength of the structural plane during shear creep were also investigated. An empirical formula is finally established to evaluate shear strength of discontinuity and a modified Burger model was proposed to represent the shear deformation property during creep.

scholarly journals Low-Temperature Annealing Induced Amorphization in Nanocrystalline NiW Alloy Films

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Z. Q. Chen ◽  
F. Wang ◽  
P. Huang ◽  
T. J. Lu ◽  
K. W. Xu
Keyword(s):  
Low Temperature ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Tem Analysis ◽  
Alloy Films ◽  
Glass Forming ◽  
Low Temperature Annealing ◽  
Transmission Electron

Annealing induced amorphization in sputtered glass-forming thin films was generally observed in the supercooled liquid region. Based on X-ray diffraction and transmission electron microscope (TEM) analysis, however, here, we demonstrate that nearly full amorphization could occur in nanocrystalline (NC) sputtered NiW alloy films annealed at relatively low temperature. Whilst the supersaturation of W content caused by the formation of Ni4W phase played a crucial role in the amorphization process of NiW alloy films annealed at 473 K for 30 min, nearly full amorphization occurred upon further annealing of the film for 60 min. The redistribution of free volume from amorphous regions into crystalline regions was proposed as the possible mechanism underlying the nearly full amorphization observed in NiW alloys.

DC Magnetron Sputtering of B2 Phase Feal(111) Single-Crystal-Like Films and Hydrogen Damage Behavior

2013 ◽  
Vol 853 ◽  
pp. 131-134
Author(s):  
Tao Tang ◽  
Yi Liu ◽  
Qun Li ◽  
Jiang Li Cao ◽  
Yu Zhe Liu ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Single Crystal ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Tem Analysis ◽  
X Ray ◽  
Hydrogen Damage ◽  
Atomic Force ◽  
Transmission Electron ◽  
B2 Phase

B2 ordered FeAl intermetallic is an important candidate for high-temperaturestructural materials, and its hydrogen embrittlement problem has attracted wide attentions in recent decades. In this paper, we prepared single-crystal-like B2-FeAl (111) thin films on Si (111) substrate using the conventional magnetron sputtering method, and studied the phase composition and the influences of hydrogen on FeAl (111) films by X-ray diffraction (XRD), scanning electron microscopy (SEM), Atomic force microscope (AFM) and transmission electron microscope (TEM) analysis. The preffered growth mechanism of FeAl (111) film and its hydrogen induced modification were discussed.

Growth Behavior of Au on Semiconductor and Insulating Substrates

1985 ◽  
Vol 47 ◽  
Author(s):  
E. I. Alessandrini ◽  
M. O. Aboelfotoh ◽  
R. B. Laibowltz ◽  
J. A. Lacey
Keyword(s):  
Single Crystal ◽  
Substrate Surface ◽  
Electron Beam Evaporation ◽  
Growth Behavior ◽  
Tem Analysis ◽  
Si Substrates ◽  
Transmission Electron ◽  
Substrate Surface Roughness ◽  
Amorphous Si ◽  
Deposition Conditions

ABSTRACTThere is a great deal of interest in forming Au grains on semiconductor and insulating substratcs for device application. Reduction in density of grain boundaries is known to cause improvement of clectromigration in thin films. Transmission electron microscopy and diffraction have been used to study the growth behavior and morphology of vapor deposited Au on these substrates. Electron beam evaporation techniques were used to evaporate Au at high rates (50Å/sec or higher) on substrates held at low temperature (Rm. Temp. to 250°C). Large Au grains laave been found to form on both amorphous (Si3N4 and SiO2) and single crystal Si substrates. The grain size of Au was also found to be dependent on substrate surface roughness; rough surfaces tended to retard the formation of large grains. Grains as large as 1/2 μ in a matrix of smaller ones were observed in films as thin as 350Å Annealing up to 350°C, subsequent to deposition, did not appreciably increase the size of the larger grains, although the smaller ones grew by about 10%. The TEM analysis together with RBS and AES data showed no significant interaction between Au and Si (that is to say no atomic intermixing or silicide formation) under all deposition conditions as well as annealing heat treatments. The significance of this in relation to the growth behavior of Au on the insulating and single crystal Si substrates will be shown.

Microstructural Evolution during Tensile Creep of a Single-Crystal Nickel-Base Superalloy

2007 ◽  
Vol 353-358 ◽  
pp. 511-514
Author(s):  
Ying Li ◽  
Hui Chen Yu ◽  
Xue Ren Wu ◽  
Xiao Guang Yang ◽  
Duo Qi Shi
Keyword(s):  
Electron Microscope ◽  
Single Crystal ◽  
Microstructural Evolution ◽  
Tensile Creep ◽  
Creep Process ◽  
Nickel Base Superalloy ◽  
Creep Tests ◽  
Transmission Electron ◽  
Nickel Base ◽  
Base Superalloy

Tensile creep tests were conducted at 980°C under a constant stress on a single crystal nickel base superalloy. Some tests were interrupted at different stages during the creep process. The strain-time curves indicated that this alloy exhibited conventional primary, steady-state and tertiary stages at this temperature. The transmission electron microscope (TEM) observations of foils taken from the gauge sections of specimens were made to interpret the microstructural evolution that occurred during the creep process. It was found that the γ′ particles were rafted in the direction perpendicular to the applied stress. The acceleration of the creep rate was related to the change of the dislocation density.

Structural Effects in Al(111)/Si(111) Heteroepitaxy by Partially Ionized Beam Deposition α

1988 ◽  
Vol 116 ◽  
pp. 465-470 ◽  
Author(s):  
A. S. Yapsir ◽  
C.-H. Choi ◽  
S. N. Yang ◽  
T.-M. Lu ◽  
M. Madden ◽  
...  
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Tem Analysis ◽  
Atom Ratio ◽  
Transmission Electron ◽  
Large Lattice ◽  
Large Lattice Mismatch ◽  
Partially Ionized ◽  
Acceleration Voltage

AbstractSingle crystal Al(111) films were grown on Si(111) surface at room temperature under a conventional vacuum condition using the partially ionized beam (PIB) deposition technique. The Al films were deposited with an ion to atom ratio of about 0.3% and an acceleration voltage of 1 kV. Transmission electron microscopy (TEM) analysis showed that the as-deposited films were single crystal with certain density of dislocation networks. These dislocations disappeared following a heat treatment at 450°C for 30 min. From X-ray diffraction and TEM patterns, it was observed that the Al(111) was aligned to the substrate with Al<1l0>//Si<1l0>. Possible mechanisms of the PIB epitaxial growth and a novel structural defect that is unique to this large lattice mismatch system are discussed.

On the nucleation of planar faults during low temperature and high stress creep of single crystal Ni-base superalloys

2018 ◽  
Vol 144 ◽  
pp. 642-655 ◽  
Author(s):  
X. Wu ◽  
A. Dlouhy ◽  
Y.M. Eggeler ◽  
E. Spiecker ◽  
A. Kostka ◽  
...  
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
High Stress
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