High Strain Rate Superplasticity in Fine-Grained Commercial Al Alloys Processed by Equal-Channel Angular Pressing

The high-strain-rate response of ultra-fine-grained (UFG) copper fabricated by equal channel angular pressing (ECAP) has been characterized by Split Hopkinson Pressure Bar (SHPB) test and quasi-static compression test has also been performed for comparison here. In the result of quasi-static tests a maximum yield stress equal to 432 MPa has been reached, at the same time the corresponding value turned out to be 995 MPa after a dynamic loading with the strain rate equal to 1700 s-1. It has been demonstrated that the strain rate sensitivity coefficient (m) has enhanced from 0.026 (coarse-grained copper) to 0.037 (UFG copper). Microstructure has indicated a high dislocation density and deformation twins inside the grains formed after a high-strain-rate deformation, which resulted in a high flow stress. The occurrence of a dynamic recrystallization has also been observed in the UFG copper subjected to high-strain-rate deformation. This has become apparent as an accelerated thermal softening and inherent instability typical for the UFG structure. Absence of adiabatic shear bands pointed out that UFG copper can be subjected to a dynamic impact without any fracture.

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High Strain Rate Superplasticity in a Zr and Sc Modified 7075 Aluminum Alloy Produced by ECAP

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.164 ◽

2008 ◽

Vol 584-586 ◽

pp. 164-169 ◽

Cited By ~ 6

Author(s):

Krystof Turba ◽

Premysl Malek ◽

Edgar F. Rauch ◽

Miroslav Cieslar

Keyword(s):

Aluminum Alloy ◽

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Rate Sensitivity ◽

7075 Aluminum Alloy ◽

Fine Grained ◽

Angular Pressing ◽

Average Grain Size ◽

Elongation To Failure

Equal-channel angular pressing (ECAP) at 443 K was used to introduce an ultra-fine grained (UFG) microstructure to a Zr and Sc modified 7075 aluminum alloy. Using the methods of TEM and EBSD, an average grain size of 0.6 1m was recorded after the pressing. The UFG microstructure remained very stable up to the temperature of 723 K, where the material exhibited high strain rate superplasticity (HSRSP) with elongations to failure of 610 % and 410 % at initial strain rates of 6.4 x 10-2 s-1 and 1 x 10-1 s-1, respectively. A strain rate sensitivity parameter m in the vicinity of 0.45 was observed at temperatures as high as 773 K. At this temperature, the material still reached an elongation to failure of 430 % at 2 x 10-2 s-1. These results confirm the stabilizing effect of the Zr and Sc additions on the UFG microstructure in a 7XXX series aluminum alloy produced by severe plastic deformation.

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Tensile Ductility of Ultra-Fine Grained Copper at High Strain Rate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.160-162.260 ◽

2010 ◽

Vol 160-162 ◽

pp. 260-266 ◽

Cited By ~ 3

Author(s):

Tao Suo ◽

Kui Xie ◽

Yu Long Li ◽

Feng Zhao ◽

Qiong Deng

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Testing Machine ◽

Coarse Grained ◽

Dislocation Dynamic ◽

Pressing Method ◽

Fine Grained ◽

Angular Pressing ◽

Split Hopkinson

In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

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Improvement of high strain rate and room temperature superplasticity in Zn–22Al alloy by two-step equal-channel angular pressing

Materials Science and Engineering A ◽

10.1016/j.msea.2014.09.114 ◽

2015 ◽

Vol 620 ◽

pp. 233-240 ◽

Cited By ~ 29

Author(s):

M. Demirtas ◽

G. Purcek ◽

H. Yanar ◽

Z.J. Zhang ◽

Z.F. Zhang

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Equal Channel Angular Pressing ◽

Room Temperature ◽

High Strain ◽

Angular Pressing

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Microstructure and Superplasticity of an Al-Mg-Sc-Zr Alloy Processed by ECAP and Subsequent Cold Rolling

Materials Science Forum ◽

10.4028/www.scientific.net/msf.830-831.345 ◽

2015 ◽

Vol 830-831 ◽

pp. 345-349 ◽

Cited By ~ 2

Author(s):

Elena Avtokratova ◽

Oleg Sitdikov ◽

Oksana Mukhametdinova ◽

Michael Markushev ◽

S.V.S. Narayana Murty ◽

...

Keyword(s):

Cold Rolling ◽

High Strain Rate ◽

Ambient Temperature ◽

Strain Rate ◽

Equal Channel Angular Pressing ◽

High Strain ◽

Strain Rates ◽

Angular Pressing ◽

Zr Alloy

The feasibility has been demonstrated for achieving high-strain-rate superplasticity with elongations beyond 2000% in Al-Mg-Sc-Zr alloy with the partially recrystallized structure, produced by warm equal-channel angular pressing to strain of e~3 only. Subsequent alloy ambient temperature rolling up to e~1.6 enhanced the superplastic elongations and moved the optimum of superplasticity toward the higher strain rates.

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Application to Seismic Dampers in High-Strain-Rate Superplastic Zn-Al Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3055 ◽

2005 ◽

Vol 475-479 ◽

pp. 3055-3060 ◽

Cited By ~ 5

Author(s):

Atsumichi Kushibe ◽

Koichi Makii ◽

L.F. Chiang ◽

Tsutomu Tanaka ◽

Masahide Kohzu ◽

...

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Work Hardening ◽

High Performance ◽

High Strain ◽

Al Alloys ◽

Al Alloy ◽

Seismic Damper ◽

Fine Grained ◽

Work Hardening Rate

High strain rate superplasticity has been realised at room temperature for the first time with a ultra fine grained Zn-22wt%Al alloy. Zn-Al alloys have some advantages over low-yieldpoint steels in their low work-hardening rate and high ductility. In addition, Zn-Al alloys are environment-conscious because of no harmful metal like Pb. However, when Zn-Al alloys are subjected to plastic deformation, the strain is localised and local fracture can take place because of their low work-hardening property. In this study, a seismic damper was designed with a Ultra fine grained Zn-Al alloy. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed.

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