A Deformation Mechanism for Ridge-Shaped Kink Structure in Layered Solids

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
Xiao-Wen Lei ◽  
Akihiro Nakatani
Keyword(s):  
Plastic Deformation ◽  
Formation Mechanism ◽  
Deformation Mechanism ◽  
Compressive Force ◽  
Deformation Mode ◽  
Strain Condition ◽  
Localized Deformation ◽  
Slip Direction ◽  
Mass Model ◽  
Kink Structure

A deformation mechanism for ridge-shaped kink structure (RSKS), a type of localized deformation, is studied with a discussion focusing on the kink deformation of a monocrystal with a single-slip system under a plane-strain condition. From a geometrical study of displacement continuity it is found that, to satisfy displacement continuity, the kink boundary formed by the deformation from an initially homogeneous structure must have symmetry. We propose a simple model of the RSKS deformation mode to accomplish plastic deformation from a compressive force parallel to the slip direction. First, important geometrical knowledge related to the RSKS formation mechanism is formulated analytically. Then, a simulation of a spring–mass model is performed to clarify the RSKS formation mechanism. The intensity of the angle-dependent force field is found to affect the deformation mode.

Deformation Mechanisms in Nanocrystalline Nickel at Low Temperatures

2011 ◽  
Vol 683 ◽  
pp. 193-201 ◽  
Author(s):  
L. Hollang ◽  
K. Reuther ◽  
S.R. Dey ◽  
E. Hieckmann ◽  
Werner Skrotzki
Keyword(s):  
Grain Size ◽  
Deformation Mechanism ◽  
Low Temperatures ◽  
Deformation Mode ◽  
Tensile Tests ◽  
Unexpected Result ◽  
Localized Deformation ◽  
Dislocation Interaction ◽  
Boundary Interaction ◽  
Electrodeposited Nickel

It is the aim of the present paper to quantify and visualise the grain size induced transition of the deformation mechanism in metal polycrystals from the conventional dislocation–dislocation interaction at large grain sizes to (probably) dislocation–grain boundary interaction in the “nano” region. Since both types of interaction are thermally activated, thermal activation analysis can be used to discriminate between them. For this purpose dynamic tensile tests with stress relaxation tests were performed on pure pulsed electrodeposited nickel with 140 nm grain size at temperatures between 4 and 320 K. The results clearly indicate the transition temperature to be around 77 K. A rather unexpected result is the existence of a second transition of the deformation mechanism, which is only observable at very low temperatures namely from the homogeneous deformation mode governed by conventional dislocation–dislocation interaction towards localized deformation by “catastrophic shear”.

Effect of Strain Amounts on Cold Compression Deformation Mechanism of Ti-55531 Alloy with Bimodal Microstructure

2021 ◽  
Vol 1035 ◽  
pp. 182-188
Author(s):  
Jian Hua Cai ◽  
She Wei Xin ◽  
Lei Li ◽  
Lei Zou ◽  
Hai Ying Yang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Mechanism ◽  
True Strain ◽  
Bimodal Microstructure ◽  
Free Zone ◽  
Β Phase ◽  
Α Phase ◽  
Initial Stage ◽  
Pile Up ◽  
Dislocation Tangle

The plastic deformation mechanism of Ti-55531 alloy with bimodal microstructure was investigated by compression testing at room temperature. The bimodal microstructure was composed of equiaxed primary α phase (αp) and transformed β (βtrans) that consisted of acicular secondary α phase (αs) and residual β phase (βr). In the initial stage of deformation, the αp grains first underwent plastic deformation, the dislocations germinated and increased, forming the dislocation loop with the dislocation free zone in αp at the true stain of 0.083. With the true strain subsequently increasing to 0.105, the dislocation tangle and dislocation pile-up occurred in αp, and a lot of dislocations were also activated in most of αs. Moreover, the dislocation density was increasing gradually in βr with the adding of strain. Finally, the dislocation pile-up and dislocation tangle appeared in αs and βr at the true strain of 0.163. The whole deformation process was coordinated by αp, αs and βr. They accommodated mutually and completed deformation together.

Short-Term Oxidation Behavior, Microstructure Evolution and Compression Behavior of Nickel-Based Superalloy GH4037 in Solid and Semi-Solid States

2022 ◽  
Vol 327 ◽  
pp. 11-25
Author(s):  
Guan Fei Xiao ◽  
Ju Fu Jiang ◽  
Ying Wang ◽  
Ying Zhe Liu ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Mechanism ◽  
Deformation Zone ◽  
Solid Particles ◽  
Isothermal Treatment ◽  
Short Term ◽  
Solid States ◽  
Nickel Based Superalloy ◽  
Semi Solid ◽  
Solid Temperature

Semi-solid processing combines the advantages of traditional forging and casting methods, so it has received much attention recently. However, the research on semi-solid behaviors of Nickel-based superalloys has been rarely reported. In order to investigate the behaviors of Nickel-based superalloy at solid and semi-solid states, oxidation experiments, isothermal treatment experiments and deformation experiments of GH4037 alloy were studied. Short-term oxidation experiments of GH4037 alloy were carried out at a solid temperature (1200 °C) and a semi-solid temperature (1360 °C). The results indicated that the oxides formed at 1200 °C were mainly composed of TiO2, Cr2O3 and a small amount of spinels NiCr2O4, while the oxides formed at 1360 °C consisted of the spinels of NiCr2O4, NiWO4 and NiMoO4 besides TiO2 and Cr2O3. Microstructure evolution of GH4037 alloy after semi-solid isothermal treatment at 1370 °C and 1380 °C was studied. The results indicated that semi-solid microstructures consisted of equiaxed solid grains and liquid phases. The average grains size and shape factor of solid grains were affected by melting mechanism and grain growth mechanism. Compression behaviors of GH4037 alloy after compressed at 1200 °C and 1360 °C were investigated. The results indicated that the flow stress of 1360 °C decreased significantly compared to that of 1200 °C. The deformation zones in the specimens were divided into three parts: the difficult deformation zone, the large deformation zone, and the free deformation zone. At 1200 °C, the deformation mechanism was plastic deformation mechanism. At 1360 °C, sliding between solid particles (SS), liquid flow (LF), flow of liquid incorporating solid particles (FLS), plastic deformation of solid particles (PDS) coexisted in the compression specimen.

Effect of Aging Treatment on Dynamic Behavior of Mg-Gd-Y Alloy

2012 ◽  
Vol 13 (2) ◽  
pp. 111-116
Author(s):  
Lin Wang ◽  
Qiao-Yun Qin ◽  
Fan Zhang ◽  
Cheng-Wen Tan
Keyword(s):  
Plastic Deformation ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Dynamic Behavior ◽  
Deformation Mechanism ◽  
Dynamic Properties ◽  
Dynamic Compression ◽  
Aging Treatment ◽  
Dislocation Slip ◽  
Plastic Deformation Mechanism

Abstract Magnesium alloy is very attractive in many industrial applications due to its low density. The structure-property relationships of the magnesium alloy under quasi-static loading have been extensively investigated. However, the dynamic behavior, particularly the mechanism of high-rate plastic deformation, of the magnesium alloy requires more in-depth investigations. In this paper, the effect of aging treatment on the quasi-static and dynamic properties of a typical rare earth Mg-Gd-Y magnesium alloy is investigated. In particular, the plastic deformation mechanism under dynamic compression loading is discussed. Split Hopkinson Pressure Bar (SHPB) was used to carry out dynamic compression tests with controllable plastic deformation by using stopper rings. The experimental results demonstrate that both static and dynamic properties of the Mg-Gd-Y alloy vary under various aging treatment conditions (under-aged, peak-aged and over-aged conditions), due to two different kinds of second phases: remnant micro size phase from solid solution treatment and nano precipitation from aging treatment. The results of microstructure characterization and statistic analysis of the metallographic phase are presented. The area fraction of the twinned grains increases due to aging treatment and dynamic loading. The main plastic deformation mechanism of the rare earth Mg-Gd-Y magnesium alloy is possibly dislocation slip, rather than twinning for the conventional AZ31 magnesium alloy under high strain rate loading.

Ductile deformation and microstructures

2021 ◽  
pp. 58-85
Author(s):  
Jean-Luc Bouchez ◽  
Adolphe Nicolas
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Elastic Deformation ◽  
Applied Stress ◽  
Deformation Mechanism ◽  
Chemical Elements ◽  
Shear Zones ◽  
Ductile Deformation ◽  
Deformation Mechanisms ◽  
Solid Materials

In contrast to the elastic deformation, which is reversible, usually neglected by field geologists but important for geophysicists working in seismology, ductile deformation is irreversible. This chapter is restricted to solid materials. Materials containing a melt fraction will be examined in Chapter 7. In the geological literature, ‘ductile’ is often used as a synonym for ‘plastic’. The latter is rather used, and will be used to specify deformation mechanisms that dominantly involve the action of dislocations. In contrast to brittle deformation, which by essence is discontinuous and highly localized (see Chapter 3), ductile deformation is generally continuous and affects large volumes of rock. However, ductile deformation may be concentrated into restricted rock volumes (or domains). Such localization is common in shear zones and/or when superplastic deformation mechanism is involved. Plastic deformation mechanisms naturally depend on temperature, magnitude of the applied stress, mineral nature and grain-size of the rocks. In upper parts of the crust, fluids are able to carry chemical elements over large distances and influence the deformation mechanisms. Micrographs of several microstructural types as well as deformation maps for olivine and calcite are given at the end of this chapter.

Effect of Underloads on Plasticity-Induced Crack Closure: A Numerical Analysis

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
F. V. Antunes ◽  
L. Paiva ◽  
R. Branco ◽  
L. P. Borrego
Keyword(s):  
Plastic Deformation ◽  
Kinematic Hardening ◽  
Crack Opening ◽  
Compressive Force ◽  
Crack Tip ◽  
Transient Behavior ◽  
Contact Forces ◽  
Local Reduction ◽  
Tip Position ◽  
Loading Parameter

The effect of underloads is mostly quantified by the averaged effect on the fatigue crack growth rate, and the transient behavior is rarely investigated. The objective of this paper is to study the mechanisms behind the effect of underloads, periodic underloads, and underloads combined with overloads. A single underload smashes the material around the crack tip, producing a depression on crack flank and a local reduction of contact forces at the minimum load. The reduction of plastic elongation behind the crack tip has an immediate effect on crack opening level, which rapidly disappears with crack propagation. The smashing associated with the compressive force occurs mainly behind the crack tip position where the underload was applied. The effect of the underload is intimately linked to reversed plastic deformation, which explains its enhanced effect for kinematic hardening. The decrease of load below the minimum baseline load is the main loading parameter. The application of periodic underloads extends the effect of a single underload. The effect of the underload is enhanced by the presence of obstacles in the form of residual plastic deformation, which explains the great effect of underloads applied after overloads.

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