Temperature and Strain Rate Dependence of Deformation-Induced Point Defect Cluster Formation in Metal Thin Foils

2001 ◽  
Vol 673 ◽  
Author(s):  
K. Yasunaga ◽  
Y. Matsukawa ◽  
M. Komatsu ◽  
M. Kiritani
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Cluster Formation ◽  
Vacancy Cluster ◽  
Long Tail ◽  
Vacancy Clusters ◽  
Thin Foils ◽  
Lower Strain ◽  
Wide Range ◽  
Deformation Speed

ABSTRACTThe mechanism of plastic deformation in thin metal foils without involving dislocations was examined by investigating the variations in vacancy cluster formation during deformation for a range of deformation speeds and temperatures. The deformation morphology was not seen to change appreciably over a very wide range of strain rate, 10-4/s – 106/s, whereas the number density of vacancy clusters was observed to increase with increasing strain rate up to saturation value that is dependent on materials and temperature. The density of vacancy clusters decreased to zero with decreasing deformation speed. The strain rate at which the density of vacancy clusters begins to decrease was found to be proportional to the vacancy mobility, suggesting that the vacancies are generated as dispersed vacancies and escape to the specimen surfaces during slow deformation without forming clusters. A very long tail in the distribution of the density of vacancy clusters towards lower strain rates was reasonably attributed to the generation of small vacancy complexes due to deformation. These results give valuable information that can be used to establish new models for plastic deformation of crystalline metals without involving dislocations.

Plastic Deformation of Thin Metal Foils without Dislocations and Formation of Point Defects and Point Defect Clusters

2001 ◽  
Vol 673 ◽  
Author(s):  
Michio Kiritani ◽  
Kazufumi Yasunaga ◽  
Yoshitaka Matsukawa ◽  
Masao Komatsu
Keyword(s):  
Plastic Deformation ◽  
Cluster Formation ◽  
Vacancy Cluster ◽  
Dislocation Mechanism ◽  
Metal Foils ◽  
Thin Foils ◽  
Stacking Fault Tetrahedra ◽  
Deformation Speed ◽  
Point Defect Clusters ◽  
Crystalline Metal

ABSTRACTEvidence for plastic deformation of crystalline metal thin foils without dislocations is presented. Direct observation during deformation under an electron microscope confirmed the absence of the operation of dislocations even for heavy deformation. In fcc metals including aluminum, deformation leads to the formation of an anomalously high density of vacancy clusters, in the form of stacking fault tetrahedra. The dependency of vacancy cluster formation on temperature and deformation speed indicates that the clusters are formed by the aggregation of deformation-induced vacancies. Conditions required for the absence of the dislocation mechanism are explained, and a new atomistic model for plastic deformation of crystalline metals is proposed.

Strain-Rate Dependence of Vacancy Cluster Size in Hydrogen-Charged Martensitic Steel AISI410 under Tensile Deformation

2017 ◽  
Vol 373 ◽  
pp. 171-175 ◽  
Author(s):  
Kazuki Sugita ◽  
Yasumasa Mutou ◽  
Yasuharu Shirai
Keyword(s):  
Strain Rate ◽  
Positron Lifetime ◽  
Tensile Deformation ◽  
Martensitic Steel ◽  
Vacancy Cluster ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Strain Rates ◽  
Vacancy Clusters ◽  
Positron Lifetime Spectroscopy

The strain-rate dependence of vacancy cluster sizes in hydrogen-charged martensitic steel AISI410 under tensile deformation was investigated using positron lifetime spectroscopy. The vacancy-cluster sizes in hydrogen-charged samples tended to increase with decreasing strain rates during the tensile deformations. The vacancy-cluster sizes significantly correlated to the tensile elongations to fracture. It was revealed that the presence of large-sized vacancy-clusters can cause the degradation of mechanical properties and followed by brittle fracture.

Investigation of Dynamic Strain Ageing Effects of Low Alloy Steels 15Kh2MFA and 15Kh2NMFA

2005 ◽  
Vol 482 ◽  
pp. 367-370
Author(s):  
Miroslava Ernestová
Keyword(s):  
Strain Rate ◽  
Tensile Tests ◽  
Dynamic Strain ◽  
Low Alloy Steels ◽  
Strain Rates ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Lower Strain ◽  
Wide Range ◽  
Alloy Steels

The paper summarizes results of tensile tests in low alloy steel (LAS) specimens (steels 15Kh2MFA and 15Kh2NMFA). Slow Strain Rate Tensile tests (SSRT) were performed in air at temperatures from 22 to 325°C over a wide range of strain rates from 2.5×10-6 to 1.67×10-3 s-1. The possible effect of strain rate and temperature to mechanical properties of tested LAS is searched for. The dynamic strain ageing (DSA) was observed within certain temperature ranges at lower strain rates tested and its hardening effect in terms of the maximum strengthening stress decreased linearly with the increase of log strain rate. It has been found that the occurrence of susceptibility to environmentally assisted cracking (EAC) of tested steels in high temperature water (HTW) is corelated to the DSA behavior. The result suggest that DSA reduces ductility of reactor pressure vessel (RPV) steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature. A reasonable coincidence was observed between the susceptibility to DSA exhibited by SSRT in air and with the EAC behavior observed in laboratory experiments.

Simulation of Vacancy Cluster Formation and Binding Energies in Single Crystal Germanium

2007 ◽  
Vol 994 ◽  
Author(s):  
Piotr Spiewak ◽  
Krzysztof Jan Kurzydlowski ◽  
Jan Vanhellemont ◽  
Piotr Wabinski ◽  
Krzysztof Mlynarczyk ◽  
...  
Keyword(s):  
Single Crystal ◽  
Cluster Formation ◽  
Vacancy Cluster ◽  
Growth Patterns ◽  
Binding Energies ◽  
Effective Surface ◽  
Vacancy Clusters ◽  
Molecular Dynamics Calculations ◽  
Weber Potential ◽  
Effective Surface Energy

AbstractResults are presented of the simulation of the properties of vacancy clusters in single crystal germanium. Classical molecular dynamics calculations based on a Stillinger and Weber potential were used in a theoretical investigation of different growth patterns of vacancy clusters Vi. The formation and binding energies of vacancy clusters have been studied in the range 1 ≤ i ≤ 35. The energetically favourable growth mode and an estimate of the effective surface energy was determined for a vacancy clusters containing up to 35 vacancies

High-Temperature Severe Plastic Deformation of Ferritic Steel by Torsion

2010 ◽  
Vol 667-669 ◽  
pp. 403-408
Author(s):  
Aries Setiawan ◽  
Daisuke Terada ◽  
Nobuhiro Tsuji
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Strain Rate ◽  
Equivalent Strain ◽  
Phase Region ◽  
Low Carbon ◽  
Ultrafine Grained ◽  
Lower Strain ◽  
Higher Temperature ◽  
Torsion Deformation

An ultra-low carbon IF steel was heavily deformed up to an equivalent strain of 36 at various high temperatures of ferrite single-phase region and various strain rates. Effects of temperature and strain rate on the microstructures evolved in torsion deformation were clarified. On the other hand, it was found that homogeneous ultrafine grained structures were not obtained by the present torsion deformation though very high strain was applied. The coarser grain sizes than those obtained by conventional severe plastic deformation (like ARB) were due to the deformation at higher temperature and lower strain rate, but lower fraction of high-angle grain boundaries in the torsion specimen was suggested to be attributed to the characteristics of monotonic torsion (or simple shear) deformation including the way of strain evaluation.

Dynamic Mechanical Responses of Ultrafine-Grained IF Steel Over a Wide Range of Temperatures

2018 ◽  
Vol 10 (04) ◽  
pp. 1850044 ◽  
Author(s):  
Jiejian Liu ◽  
Tao Suo ◽  
Yuqing Fan ◽  
Jianguo Li ◽  
Fenghua Zhou ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Temperature Rise ◽  
Shear Localization ◽  
Adiabatic Shear ◽  
Strain Rates ◽  
Interstitial Free ◽  
If Steel ◽  
Ultrafine Grained ◽  
Wide Range

The ultrafine-grained interstitial free (UFG-IF) steel was fabricated using the equal channel angular pressing (ECAP) method. Transmission electronic microscope (TEM) observations showed that the grains were refined to sub-micrometer scale and the average grain size was several hundred nanometers (nm). Uniaxial compression tests were conducted over a wide range of strain rates (up to 6000/s) and temperatures (from −196[Formula: see text]C to 300[Formula: see text]C) to understand the dependence of mechanical behaviors on the strain rate and temperature. It is found that the UFG-IF steel showed a weak strain rate sensitivity and displayed a strong temperature sensitivity only within a very narrow temperature range. Microstructural observations on the specimens deformed dynamically at temperatures below −20[Formula: see text]C via scanning electronic microscopy (SEM) and TEM indicated the occurrence of adiabatic shear localization. In order to explain the reason why adiabatic shear localization formed at the low temperatures and high strain rates, the susceptibility factor to adiabatic shear band (ASB) was estimated. It is proposed that more heat generated during the adiabatic plastic deformation process due to the enhanced flow stress of the UFG-IF steel at lower temperatures may play a dominant role in the formation of ASB. Meanwhile, the experimental results also provide strong evidence that for the UFG-IF steel the dynamic recrystallization which results from the severe plastic deformation and high temperature rise only occurs at the later stage of ASB evolution. With regard to the formation of ASB in the UFG IF steel, the localized plastic flow at a lower stress level indicates that localized deformation happens firstly and the temperature rise in the localized shearing zone leads to the final plastic instability.

scholarly journals A new method for determination of plastic deformation properties at high strain rate and its modelling

2021 ◽  
Vol 250 ◽  
pp. 01010
Author(s):  
Xiangfan Fang
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Tensile Testing ◽  
Good Prediction ◽  
Beam Model ◽  
Plastic Deformation Behavior ◽  
Wide Range ◽  
Deformation Properties ◽  
Ringing Effect

The determination of material properties under high speed loading is a challenge. The system ringing in a conventional servo-hydraulic tensile testing machine deteriorates the quality of force measurement, which makes a precise determination of yield locus, strain hardening and fracture strain difficult. In this work, the system ringing effect of the entire tensile testing system were analyzed. It was determined that the ringing of the system is location and geometry dependent. A new type of tensile sample has been developed. Beside of the usual major plastic deformation area, it has an additional elastic area, within which a locally restricted secondary minor plastic deformation takes place. This very small plastic deformation absorbs the elastic vibrations in this area. Therefore, the deformation forces can be measured by strain gauge without any ringing effect. The plastic deformation behavior of materials can be determined for a wide range of strain rate of 0.0001 - 1000 /s exactly. To explain the functionality and the physical background of the new sample, based on the equations for one-dimensional stress waves and theory of the stress wave attenuation due to dislocation motions, a simplified beam model with analytical formulations could be established und programmed in MATLAB. Verifications show a good prediction of sample geometry using this simplified model.

The Activation Parameters And The Mechanisms Of Plastic Deformation Of Al-Pd-Mn Single Quasicrystals

1998 ◽  
Vol 553 ◽  
Author(s):  
U. MessersChmidt ◽  
B. Geyer ◽  
M. Bartsch ◽  
M. Feuerbacher ◽  
K. Urban
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Activation Parameters ◽  
Friction Mechanism ◽  
Dislocation Generation ◽  
Voltage Electron ◽  
Video Recordings ◽  
Lower Strain ◽  
First Time

AbstractIn situ straining experiments on Al-Pd-Mn single quasicrystals in a high-voltage electron microscope between 675 °C and 750°C showed viscously moving dislocations with segments oriented in preferred directions. First measurements from video recordings indicate that dislocations on parallel traces move at two different velocities. For the first time, macroscopic samples were deformed in compression below 680 °C. Above a transition temperature of about 635°C for specimens of a fivefold compression axis and a strain rate of 10−5 s−1, the specimens show a yield point followed by a range of steady state deformation. Below that temperature, they are brittle. However, plastic deformation was achieved down to 555°C by using a lower strain rate and performing stress relaxation tests before the fracture stress was reached. The samples then show very strong work-hardening. The rapid decrease of the activation volume with decreasing temperature, which is characteristic of the high-temperature range, does not continue at low temperatures.The results are interpreted by dislocation generation and recovery and by the cluster friction mechanism controlling the dislocation mobility.

Microstructure Evolution of Hypereutectic Al-Si Alloy in Semi-Solid Compression Deformation

2013 ◽  
Vol 842 ◽  
pp. 122-129
Author(s):  
Yun Tao Wang ◽  
Xiao Guang Yuan ◽  
Bao Yi Yu ◽  
Hong Jun Huang
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Microstructure Evolution ◽  
Deformation Temperature ◽  
Sensitive Material ◽  
Positive Strain ◽  
Compression Deformation ◽  
Lower Strain ◽  
Fabrication Procedure ◽  
Semi Solid

The semi-solid microstructure evolution of hypereutectic Al-20Si-3Fe-1Mn-4Cu-1Mg alloy was studied by unidirectional compression deformation experiment, at a range of deformation temperature of 833K~873K and a range of strain rate of 0.1s-1~0.001s-1. The results showed that the microstructure of the reheating alloy was more spherical and fine than the microstructure of as-cast, the alloy was a positive strain rate sensitive material that the flow stress was decreased with increasing in deformation temperature and it was increased with increasing in strain rate. The mechanical properties of the alloy were hardly improved when the deformation temperature was too high to fracture the thick phase of the alloy.The lower strain rate was not only reducing the productivity but also reducing the plastic deformation. The microstructure of the alloy which the thick phase was broken fundamentally and the grain became further refinement can be obtained at 833K~853K, and at 0.1s-1~0.01s-1.It can be done that reducing the plastic deformation resistance and strengthening the fabrication procedure of the alloy.

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