Plasticity of Copper with Small Grain Size

2005 ◽  
Vol 482 ◽  
pp. 71-76 ◽  
Author(s):  
Yannick Champion ◽  
Cyril Langlois ◽  
Sandrine Guérin ◽  
Sylvie Lartigue-Korinek ◽  
P. Langlois ◽  
...  
Keyword(s):  
Grain Size ◽  
Free Path ◽  
Microstructural Analysis ◽  
Critical Length ◽  
Rate Sensitivity ◽  
Mean Free Path ◽  
Tensile Tests ◽  
Length Scale ◽  
Before And After ◽  
Elasto Plasticity

Based on the Taylor theory, a critical length scale is defined as the minimum dislocations cell size obtained at the maximum work-hardening for metals and alloys. When grain size is smaller than this length scale, corresponding also to a critical dislocation mean free path, new behaviours occur; such as ductility and strength, near perfect elasto-plasticity, high strain-rate sensitivity. Bulk samples are fabricated from Cu nanopowders (particle size 50 nm) by powder metallurgy techniques. The final grain size is comprised between the critical mean free path, evaluated at 130 nm and the size where transition to the so-called nano regime occurs (when unit dislocation no longer exists below 30 nm for Cu). Tensile tests are carried and microstructural analysis are performed before and after deformation.

Superplastic Behavior of a Cu-Cr-Zr Alloy Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 404-409
Author(s):  
Roman Mishnev ◽  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Strain Rate ◽  
Temperature Interval ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Average Grain Size ◽  
Gauge Section ◽  
Zr Alloy

A Cu-0.87%Cr-0.06%Zr alloy was subjected to equal channel angular pressing (ECAP) at a temperature of 400 °C up to a total strain of ~ 12. This processing produced ultra-fine grained (UFG) structure with an average grain size of 0.6 μm and an average dislocation density of ~4×1014 m-2. Tensile tests were carried out in the temperature interval 450 – 650 °C at strain rates ranging from 2.8´10-4 to 0.55 s-1. The alloy exhibits superplastic behavior in the temperature interval 550 – 600 °C at strain rate over 5.5´10-3 s-1. The highest elongation-to-failure of ~300% was obtained at a temperature of 575 °C and a strain rate of 2.8´10-3 s-1 with the corresponding strain rate sensitivity of 0.32. It was shown the superplastic flow at the optimum conditions leads to limited grain growth in the gauge section. The grain size increases from 0.6 μm to 0.87 μm after testing, while dislocation density decreases insignificantly to ~1014 m-2.

On the Investigation of the Portevin-Le Chatelier Effect in the Rolling of AA 5083

2016 ◽  
Vol 710 ◽  
pp. 175-180
Author(s):  
Antonello Astarita ◽  
Mariacira Liberini ◽  
Carla Velotti ◽  
Ciro Sinagra ◽  
Antonino Squillace
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Microstructural Analysis ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Rolling Process ◽  
Final Heat Treatment ◽  
Experimental Campaign ◽  
Chatelier Effect ◽  
The One

The aim of this paper is to investigate about the Portevin-Le Chatelier Effect (PLC) on a AA 5083 sheet. In order to study the minimizing of the PLC effect, three different rolling cyles have been carried out and an experimental campaign on the three different AA 5083 rolled has been carried out. In particular, the experimental campaign, to better understand the evolution of the phenomena during the rolling process, is based on: microstructural analysis, tensile tests and fractographic observations. Finally it has been found that the greater grain size the smaller the PLC effect, even if this effect cannot be totally removed, furthermore the PLC effect occurs only in the rolling direction. The best rolling cycle is the one that provide a hot rolling until 4mm, then a cold rolling up to 2mm and a final heat treatment of annealing.

scholarly journals The Effect of Heat Treatment on Dynamic Properties of an Additively Manufactured Ti-6Al-4V Alloy

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 111
Author(s):  
Shuangyin Zhang ◽  
Yunfei Wang ◽  
Tao Suo ◽  
Jin Yao ◽  
Xin Lin ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Compressive Strength ◽  
Internal Stress ◽  
Dynamic Properties ◽  
Microstructural Analysis ◽  
Rate Sensitivity ◽  
Heat Treated ◽  
Before And After ◽  
Dynamic Compressive Strength ◽  
Size And Morphology

Heat treatment processing is commonly applied for additively manufactured metal materials, since the as-fabricated material frequently exhibits high internal stress and self-cracking. In this work, a heat treatment route was applied to an additively manufactured Ti-6Al-4V alloy, and its effect on the dynamic compressive behavior was investigated. The experimental results showed that the heat treatment process not only increased the dynamic compressive strength of the material, but also induced a change of the dynamic compressive strength from isotropic to anisotropic. In addition, the strain rate sensitivity of the material was reduced by heat treatment, even though both the as-deposited and heat-treated samples demonstrated positive sensitivity to the loading rate. Microstructural analysis suggested that the grain size and morphology were the same before and after heat treatment, while the internal stress increased due to heat treatment.

Parameterization of the mean free path for inelastic scattering of fast electrons

1987 ◽  
Vol 45 ◽  
pp. 122-123
Author(s):  
R. F. Egerton ◽  
S. C. Cheng ◽  
T. Malis
Keyword(s):  
Energy Loss ◽  
Free Path ◽  
Mean Free Path ◽  
Fast Electrons ◽  
Before And After ◽  
The Mean ◽  
Convergent Beam ◽  
Inelastic Mean Free Path ◽  
Electron Energy Loss ◽  
Beam Diffraction

The areas, Iz and It, under the zero-loss peak and under the entire energy-loss spectrum (of a sample of thickness t) are related by the formula:t/ƛ(β) = ln (It/Iz) (1)where ƛ(β) is the inelastic mean free path for all energy losses and for scattering into the collection aperture, of semiangle β. We have used Eq.(l) to experimentally determine ƛ(β) by electron energy-loss spectroscopy of specimens of known composition and thickness. In the case of crystalline samples, the local thickness t was measured by convergent-beam diffraction. In the case of evaporated thin-film specimens, the average thickness was obtained by accurately weighing the substrate before and after deposition. The energy-loss spectroscopy was carried out in CTEM mode with incident energies Eo between 20keV and 120keV, and with collection semiangles in the range 0.2 mrad to 100 mrad.

Strain Rate Sensitivity of Ultrafine Grained FCC- and BCC-Type Metals

2006 ◽  
Vol 503-504 ◽  
pp. 781-786 ◽  
Author(s):  
Johannes May ◽  
Heinz Werner Höppel ◽  
Matthias Göken
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Ultrafine Grain ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained

The dependence of the strain rate sensitivity (SRS) of α-Fe and Al 99.5, as typical representatives of fcc- and bcc-type metals, on the testing temperature and with respect to the microstructure is investigated. In particular, the differences between conventional grain size (CG) and ultrafine grain size (UFG) are pointed out. UFG Al 99.5 generally shows an elevated SRS compared to CG Al 99.5. In case of α-Fe the SRS of the UFG state is decreased at room temperature, but increased at 200 °C, compared to the CG state. It is shown that the SRS also influences the ductility of UFG-metals in tensile tests.

Mechanical properties of a 20 vol % SiC whisker-reinforced, yttria-stabilized, tetragonal zirconia composite at elevated temperatures

1995 ◽  
Vol 10 (1) ◽  
pp. 113-118 ◽  
Author(s):  
S.E. Dougherty ◽  
T.G. Nieh ◽  
J. Wadsworth ◽  
Y. Akimune
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Tetragonal Zirconia ◽  
Tensile Tests ◽  
Engineering Properties ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Deformation Properties ◽  
Before And After

The high-temperature deformation behavior of a SiC whisker-reinforced, yttria-stabilized, tetragonal zirconia polycrystalline composite containing 20 vol % SiC whiskers (SiC/Y-TZP) has been investigated. Tensile tests were performed in vacuum at temperatures from 1450 °C to 1650 °C and at strain rates from 10−3 to 10−5 s−1. The material exhibits useful high-temperature engineering properties (e.g., ∼100 MPa and 16% elongation at T = 1550 °C and at a strain rate of ∼10−4 s−1). The stress exponent was determined to be n ≍ 2. Scanning electron microscopy was used to characterize the grain size and morphology of the composites, both before and after deformation. The grain size in the composite was initially fine, but coarsened at the test temperatures; both dynamic and static grain growth were observed. The morphology of ceramic reinforcements appears to affect strongly the plastic deformation properties of Y-TZP. A comparison is made between the properties of monolithic Y-TZP, 20 wt. % Al2O3 particulate-reinforced Y-TZP (Al2O3/Y-TZP), and SiC/Y-TZP composites.

scholarly journals Formability of the 5754-Aluminum Alloy Deformed by a Modified Repetitive Corrugation and Straightening Process

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 633 ◽  
Author(s):  
Marco Ezequiel ◽  
Sergio Elizalde ◽  
José-María Cabrera ◽  
Josep Picas ◽  
Ignacio A. Figueroa ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Microstructural Analysis ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Orientation Distribution ◽  
Sensitivity Coefficient ◽  
Mechanical Tests ◽  
Forming Limit

Sheets of 5754-aluminum alloy processed by a modified repetitive corrugation and straightening (RCS) process were tested in order to measure their formability. For this purpose, forming limit curves were derived. They showed that the material forming capacity decreased after being processed by RCS. However, they kept good formability in the initial stages of the RCS process. The formability study was complemented with microstructural analysis (derivation of texture) and mechanical tests to obtain the strain-rate sensitivity. The texture analysis was done by employing X-ray diffraction, obtaining pole figures, and the orientation distribution function. It was noticed that the initial texture was conserved after successive RCS passes, but the intensity dropped. RCS process did not induce β-fiber, contrary to common deformation process. The strain-rate sensitivity coefficient was measured through tensile tests at different temperatures and strain rates; the coefficient of the samples processed after one and two passes were still relatively high, indicating the capacity to delay necking, in agreement with the good formability observed in the initial passes of the RCS process.

Effect of Small Addition of Si on Superplastic Elongation at Room Temperature in Zn-Al Eutectoid Superplastic Alloy

2014 ◽  
Vol 922 ◽  
pp. 328-331 ◽  
Author(s):  
Yuhei Kamiya ◽  
Masaki Ninomiya ◽  
Tokuteru Uesugi ◽  
Yorinobu Takigawa ◽  
Kenji Higashi
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Room Temperature ◽  
Tensile Tests ◽  
Al Alloy ◽  
Superplastic Behavior ◽  
Superplastic Alloy ◽  
Average Grain Size ◽  
Before And After ◽  
Si Content

Recent experimental data have revealed that a small amount of impurity can significantly influence the superplastic behavior in Zn-Al eutectoid superplastic alloy. However, the effect of Si content on the superplastic behavior in Zn-Al alloy has not been reported. In this study, the superplastic behavior at a room temperature of two grades of the Zn-Al eutectoid superplastic alloy was studied under identical conditions of grain size, temperature, and strain rate. These two grades were prepared from high-purity Zn, Al and Al-Si alloy using the same procedure but different Si impurity levels; Zn-Al-10Si and Zn-Al-1000Si contain 10 and 900 wt. ppm of Si, respectively. As a result of annealing treatments, an average grain size of 0.6 μm in both grades. To investigate the effects of Si content on superplastic properties, the tensile tests were performed at a room temperature of 298 K and a constant strain rate of 1×10-3 s-1. Microstructures before and after the tensile tests was observed using a scanning electron microscope. The experimental results show that the elongations decreased with increasing the Si content. In contrast, the flow stress of Zn-Al alloys was not affected by the Si content. On the microstructure observation of the two grades of the Zn-Al alloy before and after the tensile tests, cavities existed at grain boundaries and strain enhanced grain growth was observed.

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