On the Anomalous Coffin-Manson Behavior Observed under Elevated Temperature Ratcheting in Type 316LN SS

2015 ◽  
Vol 830-831 ◽  
pp. 227-230 ◽  
Author(s):  
Aritra Sarkar ◽  
A. Nagesha ◽  
R. Sandhya ◽  
K. Laha
Keyword(s):  
Elevated Temperature ◽  
Fracture Mode ◽  
Deformation Mechanism ◽  
Anomalous Behavior ◽  
Positive Slope ◽  
Asymmetric Loading ◽  
316Ln Ss

Ratcheting is the progressive directional accumulation of deformation due to asymmetric loading in structures. Coffin-Manson plots derived from ratcheting experiments conducted at temperatures over the range, 823-923 K showed anomalous behavior at 873 K and 923 K in the form of dual slope and positive slope respectively, which was attributed to a change in the deformation mechanism during ratcheting in the above temperature domain. This was also reflected in the transition in the fracture mode from fatigue to creep at 873 and 923 K.

Scission and Healing in a Spinning Elastomeric Cylinder at Elevated Temperature

2002 ◽  
Vol 69 (5) ◽  
pp. 602-609 ◽  
Author(s):  
A. S. Wineman ◽  
J. A. Shaw
Keyword(s):  
Elevated Temperature ◽  
Angular Velocity ◽  
Critical Value ◽  
Anomalous Behavior ◽  
Molecular Networks ◽  
Material System ◽  
Elastomeric Material ◽  
Angular Velocities ◽  
Macromolecular Network ◽  
Temperature Responses

When an elastomeric material is subject to sufficiently high temperature, macromolecular network junctions can undergo time-dependent scission and re-crosslinking (healing). The material system then consists of molecular networks with different reference states. A constitutive framework, based on the experimental work of Tobolsky, is used to determine the evolution of deformation of a solid rubber cylinder spinning at constant angular velocity at an elevated temperature. Responses based on underlying neo-Hookean, Mooney-Rivlin, and Arruda-Boyce models, were solved numerically and compared. Different amounts of healing were studied for each case. For neo-Hookean molecular networks, there may be a critical finite time when the radius grows infinitely fast and the cylinder “blows up.” This time depends on the angular velocity and the rate of re-cross linking. In addition, no solution was possible for angular velocities above a critical value, even without the effects of scission. Such anomalous behavior does not occur for Mooney-Rivlin or Arruda-Boyce network response.

Superplastic Extrusion of Al2O3-YTZ Nanocomposite and Its Deformation Mechanism

2005 ◽  
Vol 475-479 ◽  
pp. 2973-2976 ◽  
Author(s):  
Guo Qing Chen ◽  
Kai Feng Zhang
Keyword(s):  
Elevated Temperature ◽  
Grain Growth ◽  
Deformation Mechanism ◽  
Tetragonal Zirconia ◽  
Extrusion Pressure ◽  
Second Phase ◽  
Temperature Range ◽  
Punch Speed ◽  
Dynamic Grain Growth

Using Al2O3-YTZ(3mol% yttria stabilized tetragonal zirconia) nanocomposite, superplastic extrusion under different conditions was adopted to form blade models. The results demonstrate that desired microstructure is achieved through the addition of 20mol% YTZ which acts as a second-phase pinning agent. At temperature range of 1650°C to 1700°C the material shows good deformability. At this elevated temperature the maximum extrusion pressure is lower than 25MPa, and the maximum punch speed is about 0.35mm·min-1. In superplastic extrusion the dominating deformation mechanism is grain sliding and rotation, the accommodating mechanism is intergranular zirconia coordinated deformation. Meanwhile static and dynamic grain growth also plays an important role in deformation.

Creep Damage of a Re/Ru-Containing Single Crystal Nickel-Based Superalloy at Elevated Temperature

2019 ◽  
Vol 795 ◽  
pp. 123-129
Author(s):  
Guo Qi Zhao ◽  
Su Gui Tian ◽  
Shun Ke Zhang ◽  
Ning Tian ◽  
Li Rong Liu
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Single Crystal ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Creep Damage ◽  
Stress Axis ◽  
Dislocation Configuration ◽  
Nickel Based Superalloy ◽  
Damage And Fracture

By means of creep properties measurement, microstructure observation and contrast analysis of dislocation configuration, the creep behavior of a 4.5%Re/3.0%Ru-containing single crystal nickel-based superalloy at elevated temperature is investigated. Results show that the creep life of the alloy at 1040°C/160MPa is measured to be 725h to exhibit a better creep resistance at high temperature. In the primary stage of creep at high temperature, the γ phase in alloy has transformed into the N-type rafted structure along the direction vertical to the stress axis, the deformation mechanism of alloy during steady state creep is dislocations slipping in γ matrix and climbing over the rafted γ phase. In the latter period of creep, the deformation mechanism of alloy is dislocations slipping in γ matrix and shearing into the rafted γ phase. Wherein the dislocations shearing into the γ phase may cross-slip from {111} to {100} planes for forming the K-W locks to restrain the slipping and cross-slipping on {111} plane, which is thought to be the main reason of the alloy having a better creep resistance. As the creep goes on, the alternate slipping of dislocations results in the twisted of the rafted γ phase to promote the initiation and propagation of the cracks along the interfaces of γ/γ phase up to creep fracture, which is thought to be the damage and fracture mechanism of alloy during creep at high temperature.

Microstructural Evolution of Magnesium Alloy during Hot Compression

2013 ◽  
Vol 446-447 ◽  
pp. 158-163
Author(s):  
Xing Cheng Li ◽  
Ya Lin Lu ◽  
Jiang Tao Wang ◽  
Lin Dou
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Magnesium Alloy ◽  
Dynamic Recrystallization ◽  
Process Parameters ◽  
Deformation Mechanism ◽  
Deformation Process ◽  
Hot Compression ◽  
Strain Rates ◽  
Dynamic Recrystallisation

Hot compression of AZ3l magnesium alloy was carried out at deformation temperatures of 523-723K and strain rates of 0.01-10s-1. The effects of deformation process on the microstructure and flow stress were investigated. The flow stress curves showed the characteristic of dynamic recrystallization (DRX) with deformation process parameters. Optical microscopy and TEM observations indicated that dynamic recrystallisation and twins structure were found during hot compression. Deformation mechanism of AZ3l magnesium alloy at elevated temperature was discussed in this paper.

Elevated-Temperature Mechanical Behavior of a Carbon-Manganese Pressure Vessel Steel

1977 ◽  
Vol 99 (4) ◽  
pp. 359-365
Author(s):  
J. G. Early
Keyword(s):  
Elevated Temperature ◽  
Fracture Mode ◽  
Pressure Vessel ◽  
Material Constant ◽  
Creep Rupture ◽  
Pressure Vessel Steel ◽  
Aging Effects ◽  
Stress Regime ◽  
Vessel Steel ◽  
Short Time

The short-time effects of stress and temperature on the mechanical properties of a carbon-manganese pressure vessel steel were investigated using room- and elevated-temperature tensile tests and short-time creep-rupture tests. The tensile test results indicated that strain aging effects were not Significant in the temperature range 593 to 677 C (1100 to 1250 F). Analysis of the creep-rupture data, in the range 621 to 677 (1150 to 1250 F), by the Larson-Miller method using the procedure of Manson and Mendelson yielded a value of 20.7 for the material constant, C. In the temperature and stress regime studied, a linear relationship was observed between log (stress) and log (time-to-rupture). Fractographic analyses revealed a common fracture mode in all specimens tested. The fracture mode is described as an intermediate type, containing features of both transgranular and intergranular fracture.

scholarly journals Reveal the Deformation Mechanism of (110) Silicon from Cryogenic Temperature to Elevated Temperature by Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1632
Author(s):  
Jing Han ◽  
Yuanming Song ◽  
Wei Tang ◽  
Cong Wang ◽  
Liang Fang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Elevated Temperature ◽  
Deformation Mechanism ◽  
Cryogenic Temperature ◽  
Dynamics Simulation ◽  
Structure Evolution ◽  
Load Pressure ◽  
Plastic Deformation Mechanism ◽  
Indentation Strain

Silicon undergoes a brittle-to-ductile transition as its characteristic dimension reduces from macroscale to nanoscale. The thorough understanding of the plastic deformation mechanism of silicon at the nanoscale is still challenging, although it is essential for developing Si-based micro/nanoelectromechanical systems (MEMS/NEMS). Given the wide application of silicon in extreme conditions, it is, therefore, highly desirable to reveal the nanomechanical behavior of silicon from cryogenic temperature to elevated temperature. In this paper, large-scale molecular dynamics (MD) simulations were performed to reveal the spherical nanoindentation response and plastic deformation mechanism of (110)Si at the temperature range of 0.5 K to 573 K. Special attention was paid to the effect of temperature. Multiple pop-ins detected in load/pressure-indentation strain curves are impacted by temperature. Four featured structures induced by nanoindentation, including high-pressure phases, extrusion of α-Si, dislocations, and crack, are observed at all temperatures, consistent with experiment results. The detailed structure evolution of silicon was revealed at the atomic scale and its dependence on temperature was analyzed. Furthermore, structure changes were correlated with pop-ins in load/pressure-indentation strain curves. These results may advance our understanding of the mechanical properties of silicon.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

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