scholarly journals High-Stress Compressive Creep Behavior of Ti-6Al-4V ELI Alloys with Different Microstructures

2020 ◽  
Vol 321 ◽  
pp. 11007
Author(s):  
Zhenhua Dan ◽  
Jiafei Lu ◽  
Hui Chang ◽  
Ping Qu ◽  
Aifeng Zhang ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Creep Behavior ◽  
Microstructural Analysis ◽  
High Stress ◽  
Dislocation Slip ◽  
Duplex Microstructure ◽  
Compression Tests ◽  
Compressive Creep ◽  
Burgers Vector ◽  
Dislocation Glide

Influence of initial microstructure of Ti-6Al-4V ELI alloys on their compressive creep behavior at ambient temperature was investigated with applying compression stresses from 695 to 1092 MPa The experimental results show that the basketweave alloys have better compressive creep resistances than those duplex ones. The constitutive equations in steady-state compressive creeps of duplex or basketweave structure are calculated to be =2.77×10-15(σ-710)2.1 and =2.36×10-14(σ-740)1.7 by fitting the linear regression creep curves after uniaxial compression tests. The noticeable compressive creep strains occur when the applied compression stresses are higher than the threshold stresses, i.e. 710 MPa for duplex Ti-6Al-4V ELI alloys and 740 MPa for basketweave alloys. Microstructural analysis indicates that the creep deformation of Ti-6Al-4V ELI alloys at ambient temperature is mainly controlled by dislocation slip. The creep behavior of Ti-6Al-4V ELI alloy with duplex microstructure is controlled by dislocation slip, like slip dislocations with a-type Burgers vector sliding on the basal or prismatic planes and a few c+a type dislocation sliding on the pyramidal planes. While creep mechanism for basketweave ones is dislocation glide controlled by c+a type Burgers vector sliding on the pyramidal planes and a-type sliding on the basal or prismatic planes.

Dislocations in alumina deformed by prismatic slip

1978 ◽  
Vol 36 (1) ◽  
pp. 606-607
Author(s):  
J. Cadoz ◽  
J. Castaing ◽  
J. Philibert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basal Slip ◽  
Prismatic Slip ◽  
Compression Tests ◽  
Thin Sections ◽  
Burgers Vector ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

COMPRESSIVE CREEP BEHAVIOR OF REACTORCONTROL ROD MATERIAL Ag-In-Cd ALLOY

2013 ◽  
Vol 49 (8) ◽  
pp. 1012 ◽  
Author(s):  
Hongxing XIAO ◽  
Chongsheng LONG ◽  
Le CHEN ◽  
Bo LIANG
Keyword(s):  
Creep Behavior ◽  
Compressive Creep

scholarly journals Application of the Strain Compensation Model and Processing Maps for Description of Hot Deformation Behavior of Metastable β Titanium Alloy

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2021
Author(s):  
Oleksandr Lypchanskyi ◽  
Tomasz Śleboda ◽  
Aneta Łukaszek-Sołek ◽  
Krystian Zyguła ◽  
Marek Wojtaszek
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Flow Behavior ◽  
Microstructural Analysis ◽  
Calculated Data ◽  
Processing Temperature ◽  
Processing Maps ◽  
Compression Tests ◽  
Strain And Strain Rate ◽  
Average Absolute Relative Error

The flow behavior of metastable β titanium alloy was investigated basing on isothermal hot compression tests performed on Gleeble 3800 thermomechanical simulator at near and above β transus temperatures. The flow stress curves were obtained for deformation temperature range of 800–1100 °C and strain rate range of 0.01–100 s−1. The strain compensated constitutive model was developed using the Arrhenius-type equation. The high correlation coefficient (R) as well as low average absolute relative error (AARE) between the experimental and the calculated data confirmed a high accuracy of the developed model. The dynamic material modeling in combination with the Prasad stability criterion made it possible to generate processing maps for the investigated processing temperature, strain and strain rate ranges. The high material flow stability under investigated deformation conditions was revealed. The microstructural analysis provided additional information regarding the flow behavior and predominant deformation mechanism. It was found that dynamic recovery (DRV) was the main mechanism operating during the deformation of the investigated β titanium alloy.

scholarly journals Behavior of Offshore Pile in Calcareous Sand—Case Study

2021 ◽  
Vol 9 (8) ◽  
pp. 839
Author(s):  
Tarek N. Salem ◽  
Nadia M. Elkhawas ◽  
Ahmed M. Elnady
Keyword(s):  
Load Capacity ◽  
High Stress ◽  
Embedment Depth ◽  
Shear Stresses ◽  
Northern Coast ◽  
Compression Tests ◽  
Calcareous Sand ◽  
Element Analysis ◽  
Mixing Ratios

The erosion of limestone and calcarenite ridges that existed parallel to the Mediterranean shoreline forms the calcareous sand (CS) formation at the surface layer of Egypt's northern coast. The CS is often combined with broken shells which are considered geotechnically problematic due to their possible crushability and relatively high compressibility. In this research, CS samples collected from a site along the northern coast of Egypt are studied to better understand its behavior under normal and shear stresses. Reconstituted CS specimens with different ratios of broken shells (BS) are also investigated to study the effect of BS ratios on the soil mixture strength behavior. The strength is evaluated using laboratory direct-shear and one-dimensional compression tests (oedometer test). The CS specimens are not exposed to significant crushability even under relatively high-stress levels. In addition, a 3D finite element analysis (FEA) is presented in this paper to study the degradation offshore pile capacity in CS having different percentages of BS. The stress–strain results using oedometer tests are compared with a numerical model, and it gave identical matching for most cases. The effects of pile diameter and embedment depth parameters are then studied for the case study on the northern coast. Three different mixing ratios of CS and BS have been used, CS + 10% BS, CS + 30% BS, and CS + 50% BS, which resulted in a decrease of the ultimate vertical compression pile load capacity by 8.8%, 15%, and 16%, respectively.

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

2002 ◽  
Vol 17 (5) ◽  
pp. 991-1001 ◽  
Author(s):  
X. Y. Qin ◽  
J. S. Lee ◽  
C. S. Lee
Keyword(s):  
Yield Strength ◽  
Mechanical Behavior ◽  
Light Emission ◽  
Hot Isostatic Pressing ◽  
Microstructural Analysis ◽  
High Strength ◽  
Compression Tests ◽  
Mechanochemical Method ◽  
Force Microscopy ◽  
Bulk Nanocrystalline

The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.

Silicon nitride compressive creep behavior in argon atmosphere

2008 ◽  
Vol 485 (1-2) ◽  
pp. 422-427
Author(s):  
Cosme Roberto Moreira da Silva ◽  
Flaminio Levy Neto ◽  
José Alexander Araújo ◽  
Claudinei dos Santos
Keyword(s):  
Silicon Nitride ◽  
Creep Behavior ◽  
Argon Atmosphere ◽  
Compressive Creep

Compressive creep behavior of an electric brush-plated nanocrystalline Cu at room temperature

2009 ◽  
Vol 106 (8) ◽  
pp. 086105 ◽  
Author(s):  
Guoyong Wang ◽  
Jianshe Lian ◽  
Zhonghao Jiang ◽  
Liyuan Qin ◽  
Qing Jiang
Keyword(s):  
Creep Behavior ◽  
Room Temperature ◽  
Compressive Creep

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.

Analysis on the Creep Mechanism of 12Cr-Mo-W-0.25V Steel Based on Long-Term Stress Relaxation Test Data

2016 ◽  
Vol 853 ◽  
pp. 158-162
Author(s):  
Jie Zhao ◽  
Tie Shan Cao ◽  
Cong Qian Cheng ◽  
Hui Fang Li
Keyword(s):  
Stress Relaxation ◽  
Test Data ◽  
Activation Volume ◽  
High Stress ◽  
Relaxation Curve ◽  
Relaxation Test ◽  
Dislocation Slip ◽  
Stress Relaxation Test ◽  
Steel Base

The current paper investigates on the creep behavior of 12Cr-Mo-W-0.25V heat resistant steel base on the long-term stress relaxation test data. It is shows that the stress relaxation curve can be divided into 2 stages: the high stress stage has higher apparent activation volume of 79~350 b3 and the low stress stage is 35~78 b3. Besides, the Helmholtz free energy at the high stress stage is 827~1034 kJ/mol which is higher than 210~252 kJ/mol of the low stress stage. Taking both apparent activation volume and activation energy into account, it is assumed that the high stress stage is mainly controlled by dislocation slip and the low stress stage is more related to diffusion.

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