Structure Evolution and Deformation Mechanisms in Ultrafine-Grained Aluminum under Tension at Room Temperature

Deformation mechanisms occurring by tension of ultrafine-grained aluminum processed by equal-channel angular pressing at room temperature are investigated using comparative study of the microstructure before and after tensile testing as well as deformation relief on the pre-polished surface of the sample tested. Deformation behavior and structure evolution during tension suggest development of grain boundary sliding in addition to intragrain dislocation slip. Contribution grain boundary sliding to the overall deformation calculated using the magnitude of shift of grains relative to each other is found to be ~40%.

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Superplastic Behavior of Ultrafine Grained Al Alloys Fabricated by Severe Plastic Deformation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.345-346.597 ◽

2007 ◽

Vol 345-346 ◽

pp. 597-600

Author(s):

Duck Young Hwang ◽

Kion Kwon ◽

Dong Hyuk Shin ◽

Kyung Tae Park ◽

Young Gun Ko ◽

...

Keyword(s):

Grain Boundary ◽

Effective Strain ◽

Deformation Mode ◽

Grain Boundary Sliding ◽

Al Alloys ◽

Deformation Mechanisms ◽

Al Alloy ◽

Angular Pressing ◽

Ultrafine Grained ◽

Boundary Sliding

Ultrafine grained (UFG) 5083 Al and 5154 Al alloys were prepared by equal channel angular pressing (ECAP) with an effective strain of ~ 4 or ~ 8. This investigation was aimed at examining the effect of the ECAP strain and post-rolling inducing different microstructure in these alloys on the deformation mechanisms at low temperature superplastic (LTS) and high strain superplastic (HSRS) regimes. The sample after 4 passes (a strain of ∼ 4) did not exhibit LTS, but superplastic elongations were obtained in the sample after 8 passes (a strain of ∼ 8). An analysis of the mechanical data in light of the standard deformation mechanisms revealed that deformation of the sample after 4 passes was governed by dislocation climb while grain boundary sliding attributed to LTS of the sample after 8 passes. In addition, the 5154 Al alloy processed by ECAP and postrolling was capable of enhancing HSRS elongation significantly. An analysis revealed that the deformation mode was changed from dislocation viscous glide to grain boundary sliding by additional ECAP strain and post-rolling.

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A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.291-294.1173 ◽

2011 ◽

Vol 291-294 ◽

pp. 1173-1177

Author(s):

Zi Ling Xie ◽

Lin Zhu Sun ◽

Fang Yang

Keyword(s):

Grain Boundary ◽

Strain Rate ◽

Deformation Behavior ◽

Boundary Diffusion ◽

Rate Sensitivity ◽

Grain Boundary Sliding ◽

Dislocation Slip ◽

Deformation Response ◽

Ultrafine Grained ◽

Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

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Compressive Behavior of Ultrafine-Grained Mg-Zn-Y-Zr Alloy Containing Quasicrystalline Phase

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.287 ◽

2008 ◽

Vol 584-586 ◽

pp. 287-292

Author(s):

Ming Yi Zheng ◽

S.W. Xu ◽

Wei Min Gan ◽

Kun Wu ◽

Shigeharu Kamado ◽

...

Keyword(s):

Grain Boundary ◽

Grain Boundary Sliding ◽

Quasicrystalline Phase ◽

Strain Rates ◽

Temperature Range ◽

Angular Pressing ◽

Ultrafine Grained ◽

Boundary Sliding ◽

Compressive Testing ◽

Zr Alloy

An ultrafine-grained (UFG) Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr magnesium alloy with a grain size of about 0.8 µm was produced by subjecting the extruded alloy to equal channel angular pressing (ECAP) for 8 passes at 473 K. Compressive testing was performed on the ECAPed alloy in a temperature range from 423 K to 523 K and under strain rates from 1.67×10-3 to 1.67×10-1 s-1. The ultrafine grains of the ECAPed alloy were stable during compression because of the presence of the dispersion of a fine quasicrystal I-phase and of precipitates in the alloy, which restricted grain growth. The activation energy for the compression at the temperature range from 423 K to 523 K is close to the value for grain boundary diffusion in magnesium, indicating that the compressive deformation is mainly controlled by grain-boundary sliding.

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Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.449-452.665 ◽

2004 ◽

Vol 449-452 ◽

pp. 665-668 ◽

Cited By ~ 25

Author(s):

Junichi Koike

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Deformation Mechanism ◽

Room Temperature ◽

Grain Boundary Sliding ◽

Mg Alloys ◽

Deformation Mechanisms ◽

Slip Systems ◽

Dislocation Plasticity ◽

Boundary Sliding

Deformation mechanisms of Mg-Al-Zn (AZ31) alloys were investigated by performing tensile test at room temperature. In fine grain Mg alloys deformed at room temperature, nonbasal slip systems were found to be active as well as basal slip systems because of grain-boundary compatibility effect. Slip-induced grain-boundary sliding occurred as a complementary deformation mechanism to give rise to c-axis component of strain. With increasing grain size, the activation of the nonbasal slip systems was limited near grain boundaries. Instead of grain-boundary sliding, twinning occurred as a complementary deformation mechanism in large grained samples. Orientation analysis of twins indicated that twinning is induced by stress concentration due to the pile up of basal dislocations. The grain-size dependence on deformation mechanism was found to affect yielding behavior both microscopically and macroscopically which can influence various mechanical properties such as fatigue and creep.

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