The effect of hydrogen disorder on dislocation movement and plastic deformation of ice

1968 ◽  
Vol 7 (1) ◽  
pp. 43-51 ◽  
Author(s):  
J. W. Glen
Keyword(s):  
Plastic Deformation ◽  
Dislocation Movement

The Mechanical Properties of Si+ and Pb+ Implanted Al

1983 ◽  
Vol 27 ◽  
Author(s):  
P.B. Madakson
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Wear Resistance ◽  
Precipitation Hardening ◽  
Surface Oxidation ◽  
Linear Increase ◽  
Commercially Pure ◽  
Dislocation Movement ◽  
Dose Dependent ◽  
Al Matrix

ABSTRACTCommercially pure Al was implanted with 300 keV Si+ and 200 keV Pb+ to doses of between l011 and 1017 ions/cm2. Changes in friction, wear, oxidation and hardness were investigated. Silicon increased the hardness and wear resistance of Al and significantly decreased friction and the oxidation of the implanted surface. These changes were observed to be almost proportional to the implanted dose. The implantation of Pb+ resulted in a linear increase in hardness and a decrease in surface oxidation with dose. Friction decreased and wear resistance increased but the changes were not dose dependent. The implantation of Si+ did not significantly alter the distribution of impurities, such as Fe and Cu within the Al matrix, but Pb+ resulted in a diffusion of Fe to the implanted surface. Formation of precipitates was observed and the improvements in the surface properties studied are considered to result from precipitation hardening, which involves the impediment of dislocation movement by the precipitates during plastic deformation of the implanted Al.

scholarly journals Atomistic Simulation of Microstructural Evolution of Ni50.8Ti Wires during Torsion Deformation

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 92
Author(s):  
Shan Liu ◽  
Yao Lin ◽  
Tao Wu ◽  
Guangchun Wang
Keyword(s):  
Plastic Deformation ◽  
Martensitic Transformation ◽  
Microstructural Evolution ◽  
Grain Morphology ◽  
Large Degree ◽  
Atomic Scale ◽  
Main Mechanism ◽  
Grain Rotation ◽  
Dislocation Movement ◽  
Torsion Deformation

To explore the microstructural evolution of Ni50.8Ti wires during torsion deformation, single and polycrystalline models with various grain sizes (d = 9 nm, 5.6 nm, and 3.4 nm) were established on an atomic scale to explore their grain morphology evolution, stress-induced martensitic transformation, and dislocation movement. The results indicated that the grains were rotated and elongated to form long strips of grains during the torsion simulation. With the increase in torsion deformation, the elongated grains were further split, forming smaller grains. Stress-induced martensitic transformation took place and the martensite preferentially nucleated near the grain boundary, resulting in the formation of 30% austenites and 50% martensites. Additionally, a certain number of dislocations were generated during the torsion simulation. Under a low degree of torsion deformation, the main mechanism of plastic deformation was dislocation movement, while with a large degree of torsion deformation, the main mechanism of plastic deformation was grain rotation.

Effect of the Pre-Strain on the Elastic Behavior of a Dual-Phase Steel with Different Martensite Contents

2021 ◽  
Vol 1016 ◽  
pp. 1555-1560
Author(s):  
Matthias Wallner ◽  
Reinhold Schneider ◽  
Katharina Steineder ◽  
Daniel Krizan ◽  
Thomas Hebesberger ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Elastic Modulus ◽  
Modulus Of Elasticity ◽  
Volume Fraction ◽  
Hardness Test ◽  
Martensite Phase ◽  
Elastic Behavior ◽  
Present Contribution ◽  
Martensite Volume Fraction ◽  
Dislocation Movement

The modulus of elasticity is an important parameter for an accurate prediction of the springback in sheet metal forming processes. With increasing plastic deformation, this modulus behaves nonlinearly and declines, which leads to an unpredictable springback behavior. The most cited reason for this nonlinearity is the dislocation movement during plastic deformation that especially occurs with multiphase steels. The present contribution investigates the nonlinear unloading behavior and the resulting decrease of the elastic modulus from a differently heat treated DP980 steel. The heat treatments set five different microstructures with martensite volume fractions in the range of 42 to 95 %. By means of the tensile test, a decline of the elastic modulus according to pre-strain was examined by evaluating the chord-modulus during unloading at different strain levels. In addition, a nano-hardness test was performed. It turned out that in all heat treatment conditions, a pronounced decrease in the modulus of elasticity up to 25% from the initial value occurred. With decreasing annealing temperature and lower martensite volume fraction, respectively, the martensite hardness increased, leading to higher hardness differences between the ferrite and the martensite phase in the microstructure. This led to an increase of strain hardening, i.e. to an increased formation of fresh mobile dislocations in the vicinity of the harder martensite phase during plastic deformation. As a result, the modulus of elasticity decreased more sharply. Thus, in the present contribution, an interplay between the martensite volume fraction and its hardness on the decrease of elastic modulus could be clearly manifested.

Defect microstructures in garnet, omphacite and symplectite from UHP eclogites, eastern Dabieshan, China: a TEM and FTIR study

2008 ◽  
Vol 72 (5) ◽  
pp. 1057-1069 ◽  
Author(s):  
Xiuling Wu ◽  
Dawei Meng ◽  
Xiaoyu Fan ◽  
Xin Meng ◽  
Jianping Zheng ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Slip System ◽  
Early Stage ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Structural Water ◽  
Deformation Structures ◽  
Dislocation Movement ◽  
Defect Microstructures ◽  
Water Contents

AbstractGarnets, omphacite and the minerals of a clinopyroxene/amphibole/plagioclase symplectite in UHP eclogites from Yingshan, Dabieshan have been investigated by TEM and Micro-FTIR. TEM reveals that the predominant microstructures in eclogites and symplectite-forming minerals are chain multiplicity faults (CMFs), dislocation substructures, clusters of water molecules up to ∼50 nm in diameter and recrystallized grains ∼1.75 μm in diameter. This indicates dynamic recrystallization of omphacite, probably during an eclogite-facies metamorphic episode. The deformation structures in symplectite-forming minerals were produced by plastic deformation related to an amphibolite-facies retrograde metamorphic event. CMFs described in the present work demonstrate the existence of an infrequent ½<011> (010) slip system for P2/n omphacite from an UHP eclogite sample from Dabieshan. The frequent occurrence of CMFs in omphacite suggests that they indicate an important deformation mechanism in omphacite and shows that this slip system plays a significant role in the deformation and recovery of eclogite. The hydrous components of deformed minerals may cause plastic deformation of the rocks by dislocation movement and accelerate retrograde metamorphism. Micro-FTIR results show that all the garnets and omphacites contain structural water occurring as hydroxyl groups (OH) or water (H2O). The structural water contents in omphacite range from 110—710 ppm and in garnet from 0—180 ppm. Water released during decompression might supply an early-stage retrograde metamorphic fluid.

Grain Refinement and Strengthening of Aluminum Alloys: Cold Severe Plastic Deformation Model

2019 ◽  
Author(s):  
Xiao Guang Qiao ◽  
Nong Gao ◽  
Marco Starink
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Grain Refinement ◽  
Aluminium Alloys ◽  
Cold Deformation ◽  
Al Alloys ◽  
Deformation Model ◽  
Angular Pressing ◽  
Dislocation Movement ◽  
Very High

This paper presents a model which quantitatively predicts grain refinement and strength/hardness of Al alloys after very high levels of cold deformation through processes including cold rolling, equal channel angular pressing (ECAP), multiple forging (MF), accumulative rolling bonding (ARB) and embossing. The model deals with materials in which plastic deformation is exclusively due to dislocation movement, which is in good approximation the case for aluminium alloys. In the early stages of deformation, the generated dislocations are stored in grains and contribute to overall strength. With increase in strain, excess dislocations form and/or move to new cell walls/grain boundaries and grains are refined. We examine this model using both our own data as well as the data in the literature. It is shown that grain size and strength/hardness are predicted to a good accuracy.

The Role of Plastic Deformation in the Process of Powder Sintering

2006 ◽  
Vol 114 ◽  
pp. 199-210 ◽  
Author(s):  
Yu.V. Milman ◽  
Alexander N. Slipenyuk
Keyword(s):  
Plastic Deformation ◽  
Hot Deformation ◽  
Dislocation Mobility ◽  
Sintering Process ◽  
Powder Sintering ◽  
Dislocation Movement ◽  
Temperature Ranges ◽  
Important Constituent ◽  
Main Factor

It is generally supposed that diffusion is the main factor controlling the process of powder sintering. In this work it is shown that plastic deformation achieved by means of dislocation movement is also an important constituent of the sintering process. Since temperature essentially affects dislocation mobility, the temperature ranges of cold, warm and hot deformation are discussed. The stresses occurring on powder sintering leading to plastic deformation of the material are estimated. On the base of results recommendations are made for selecting the optimal condition for the sintering of powders.

Sem Examinations of Glass Knives

1970 ◽  
Vol 28 ◽  
pp. 282-283
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Tensile Loading ◽  
Resultant Force ◽  
Stress Concentrations ◽  
Edge Chipping ◽  
Surface Flaws ◽  
Edge Defects ◽  
Microscopic Surface

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

Sign in / Sign up

Export Citation Format

Share Document