Strain Rate Contribution due to Dynamic Recovery of Ultrafine-Grained Cu–Zr as Evidenced by Load Reductions during Quasi-Stationary Deformation at 0.5 Tm

During quasi-stationary tensile deformation of ultrafine-grained Cu-0.2 mass%Zr at 673 K and a deformation rate of about e - 4 / s load changes were performed. Reductions of relative load by more than about 25% initiate anelastic back flow. Subsequently, the creep rate turns positive again and goes through a relative maximum. This is interpreted by a strain rate component ϵ ˙ - associated with dynamic recovery of dislocations. Back extrapolation indicates that ϵ ˙ - contributes the same fraction of ( 20 ± 10 ) % to the quasi-stationary strain rate that has been reported for coarse-grained materials with high fraction of low-angle boundaries; this suggests that dynamic recovery of dislocations is generally mediated by boundaries. The influence of anelastic back flow on ϵ ˙ - is discussed. Comparison of ϵ ˙ - to the quasi-stationary rate points to enhancement of dynamic recovery by internal stresses. Subtraction of ϵ ˙ - from the total rate yields the rate component ϵ ˙ + related with generation and storage of dislocations; its activation volume is in the order expected from the classical theory of thermal glide.

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Tensile Deformation Behaviors of Ultrafine Grained Al-Fe-Si Alloy Sheets

Materials Science Forum ◽

10.4028/www.scientific.net/msf.512.85 ◽

2006 ◽

Vol 512 ◽

pp. 85-90 ◽

Cited By ~ 2

Author(s):

Hyoung Wook Kim ◽

Suk Bong Kang ◽

Nobuhiro Tsuji ◽

Yoritoshi Minamino

Keyword(s):

Strain Rate ◽

Dynamic Recovery ◽

Tensile Deformation ◽

Total Elongation ◽

High Angle ◽

Roll Bonding ◽

Fine Grained ◽

Tensile Deformation Behavior ◽

Ultrafine Grained ◽

Deformation Behaviors

Ultra-fine grained AA8011 alloy sheets manufactured by the accumulative roll-bonding (ARB) process exhibited unique tensile deformation behavior. Tensile strength of the ARB processed AA8011 sheets increased up to three cycles, but then showed nearly the same value after three cycles. Meanwhile, the total elongation grew significantly with an increasing nember of ARB cycles. It was found that the strain-rate sensitivities (m) of the AA8011 sheets increased up to 0.047 by the ARB process. A large number of high-angle boundaries were introduced by the ARB process and the fraction of high-angle boundaries reached 70% after eight ARB cycles. In this paper, we discusse the increase in total elongation on the basis of strain-rate sensitive deformation of the material, which is also correlated with dynamic recovery.

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The effect of strain rates on tensile deformation of ultrafine-grained copper

International Journal of Modern Physics B ◽

10.1142/s0217979217440143 ◽

2017 ◽

Vol 31 (16-19) ◽

pp. 1744014

Author(s):

M. Li ◽

Q. W. Jiang

Keyword(s):

Strain Rate ◽

Deformation Behavior ◽

Room Temperature ◽

Tensile Deformation ◽

Strain Rates ◽

Roll Bonding ◽

Fracture Elongation ◽

Tensile Deformation Behavior ◽

Ultrafine Grained ◽

Flow Stress Level

Tensile deformation behavior of ultrafine-grained (UFG) copper processed by accumulative roll-bonding (ARB) was studied under different strain rates at room temperature. It was found that the UFG copper under the strain rate of 10[Formula: see text] s[Formula: see text] led to a higher strength (higher flow stress level), flow stability (higher stress hardening rate) and fracture elongation. In the fracture surface of the sample appeared a large number of cleavage steps under the strain rate of 10[Formula: see text] s[Formula: see text], indicating a typical brittle fracture mode. When the strain rate is 10[Formula: see text] or 10[Formula: see text] s[Formula: see text], a great amount of dimples with few cleavage steps were observed, showing a transition from brittle to plastic deformation with increasing strain rate.

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New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0180 ◽

2015 ◽

Vol 60 (2) ◽

pp. 605-614 ◽

Cited By ~ 2

Author(s):

T. Kvačkaj ◽

A. Kováčová ◽

J. Bidulská ◽

R. Bidulský ◽

R. Kočičko

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Tensile Tests ◽

Coarse Grained ◽

Wear Behaviour ◽

Ofhc Copper ◽

Strain Rates ◽

Ultrafine Grained ◽

Reduction Of Area ◽

Pin On Disk

AbstractIn this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates$({\dot \varepsilon} \sim 10^2 \;{\rm{s}}^{ - 1} )$. However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.

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Strain-Rate Dependence of Compressive Yield Strength of Titanium Grade 4 with Coarse-Grained and Ultrafine-Grained Structures: Experimental Results and Theoretical Calculation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1145.100 ◽

2018 ◽

Vol 1145 ◽

pp. 100-105

Author(s):

Ivan V. Smirnov ◽

Alexander Y. Konstantinov

Keyword(s):

Yield Strength ◽

Strain Rate ◽

Yield Stress ◽

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Pure Titanium ◽

Coarse Grained ◽

Strain Rates ◽

Ultrafine Grained ◽

Titanium Grade

The nanocrystalline (NC) and ultrafine-grained (UFG) structures of metallic materials can lead to their extraordinary high strength. However, most of the papers on this topic consider deformation parameters of NC and UFG materials only for the case of quasi-static tensile tests. Characteristics of dynamic strength and fracture of such materials remain unexplored. This paper presents a study of the mechanical behavior of pure titanium Grade 4 with a coarse-grained (CG) and UFG structure under uniaxial compression with different strain rates. The UFG structure was provided using the method of equal-channel angular pressing. The dynamic compression was carried out on a setup with the Split-Hopkinson pressure bar. It is found that in the observed range of strain rates 10–3-3×103 s–1, the yield stress of the CG titanium increases by 20%, and does not exceed the yield stress of the UFG titanium. However, the yield stress of the UFG titanium remains close to a quasi-static value. It is shown that these strain-rate dependencies of the yield strength can be predicted by the incubation time approach. The calculated curves show that at strain rates above 104 s–1 the yield stress of the CG titanium becomes higher than the yield strength of the UFG titanium.

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Tensile Deformation Behavior at High Strain Rate for Ultrafine-grained Ferrite cementite Steels

Tetsu-to-Hagane ◽

10.2355/tetsutohagane1955.90.12_1043 ◽

2004 ◽

Vol 90 (12) ◽

pp. 1043-1049 ◽

Cited By ~ 14

Author(s):

Noriyuki TSUCHIDA ◽

Yo TOMOTA ◽

Kotobu NAGAI

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Deformation Behavior ◽

High Strain ◽

Tensile Deformation ◽

Tensile Deformation Behavior ◽

Ultrafine Grained

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Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size

10.20944/preprints201710.0019.v1 ◽

2017 ◽

Author(s):

Jiangjiang Hu ◽

Weiming Sun ◽

Taihua Zhang ◽

Yusheng Zhang

Keyword(s):

Grain Size ◽

Strain Rate ◽

Room Temperature ◽

Indentation Depth ◽

Dislocation Motion ◽

Coarse Grained ◽

Ultrafine Grained ◽

Pile Up ◽

Different Grain Size ◽

Multiple Slips

At room temperature, the indentation morphologies of crystalline copper with different grain size including nanocrystalline (NC), ultrafine-grained (UFG) and coarse-grained (CG) copper were studied by nanoindentation at the strain rate of 0.04/s without holding time at indentation depth of 2000 nm. As the grain size increasing, the height of the pile-up around the residual indentation increases and then has a slightly decrease in the CG Cu, While the area of the pile-up increases constantly. Our analysis has revealed that the dislocation motion and GB activities in the NC Cu, some cross- and multiple-slips dislocation insides the larger grain in the UFG Cu, and forest dislocations from the intragranular Frank-Read sources in the CG Cu, would directly induce these distinct pile-up effect.

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Microstructural Characterizations of Cu Processed by ECAP from 4 to 24 Passes

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.333 ◽

2008 ◽

Vol 584-586 ◽

pp. 333-337 ◽

Cited By ~ 21

Author(s):

Chong Xiang Huang ◽

Hua Jie Yang ◽

Shi Ding Wu ◽

Zhe Feng Zhang

Keyword(s):

Grain Boundary ◽

Dynamic Recovery ◽

High Angle ◽

Double Peak ◽

Angular Pressing ◽

Ultrafine Grained ◽

High Fraction ◽

Dislocation Cells ◽

The Many ◽

Pure Cu

The microstructures of pure Cu processed by equal channel angular pressing (ECAP) from 4 to 24 passes were investigated. It was found that the microstructures of Cu samples with a small number of ECAP passes (4-8) were not inhomogeneous and the fraction of high-angle grain boundary (HAGB) was low (25~43%). While for the samples with many number of ECAP passes (12-24), the grains became more equiaxed-like and the GB misorientations exhibited double-peak distribution with high fraction (51~64%) of HAGB. It was dislocation cells formed in large grains of the few-pass samples, but subgrains in the many-pass samples. These characterizations suggested that ultrafine-grained (UFG) microstructures in the few-pass samples were not fully accomplished, while it was obtained after many passes (>12). It is believed that dynamic recovery during processing for many passes was attributed to the formation of UFG microstructures.

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In Situ Testing and Heterogeneity of UFG Cu at Elevated Temperatures

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1127.67 ◽

2015 ◽

Vol 1127 ◽

pp. 67-72

Author(s):

Martin Petrenec ◽

Petr Král ◽

Jiří Dvořák ◽

Milan Svoboda ◽

Vàclav Sklenička

Keyword(s):

Elevated Temperature ◽

Tensile Test ◽

Grain Growth ◽

Elevated Temperatures ◽

Tensile Deformation ◽

Constant Strain Rate ◽

Electron Back Scatter Diffraction ◽

Coarse Grained ◽

Ultrafine Grained

Experiments were conducted to investigate deformation-induced processes during in-situ tensile test at elevated temperature. Consequently the microstructure after creep loading was examined by 3D Electron Back Scatter Diffraction (EBSD) technique. The billets of coarse-grained copper were processed by equal-channel angular pressing (ECAP) at room temperature using a die that had an internal angle of 90° between the two parts of the channel and an outer arc of curvature of ~ 20°, where these two parts intersect. The pressing speed was 10 mm/min. To obtain an ultrafine-grained (UFG) material, the billets were subsequently pressed by route Bc by 8 ECAP passes to give the mean grain size ~ 0.7 μm. The constant strain-rate test in tension was performed at 473 K using testing GATAN stage Microtest 2000EW with EH 2000 heated grips which is configured for in-situ electron back scatter diffraction (EBSD) observations. Microstructure was examined by FEG-SEM TESCAN MIRA 3 XM equipped by EBSD detector HKL NordlysMax from OXFORD INSTRUMENT. The tensile test was interrupted by fast stress reductions after different deformation step and observation of microstructure changes was performed. Despite of a considerable interest in ECAP processing method, there are not many works documenting microstructure evolution and changes during creep testing and determining creep mechanisms of ultrafine-grained materials processed by ECAP. It was found that creep resistance of UFG pure Al and Cu is considerably improved after one ECAP pass in comparison with coarse grained material, however, further repetitive pressing leads to a noticeable deterioration in creep properties of ECAP material. Recently it was observed the coarsening of the grains in microstructure of ECAP copper during creep at elevated temperature. It was suggested that creep behaviour is controlled by storage and dynamic recovery of dislocations at high-angle boundaries. In the present work was found that ultrafine-grained microstructure is instable and significant grain growth has already occurred during heating to the testing temperature. Static recrystallization during heating led to the formation of high fraction of special boundaries Σ3 and Σ9. The tensile deformation at 473 K led to the additional grain growth and formation of new grains. Microstructure was investigated also by 3D EBSD.

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