The definition of characteristic times of plastic relaxation by dislocation slip and grain boundary sliding in copper and nickel

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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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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Slip Induced Strain Rate Sensitivity for Superplastic Material?

Materials Science Forum ◽

10.4028/www.scientific.net/msf.735.31 ◽

2012 ◽

Vol 735 ◽

pp. 31-36 ◽

Cited By ~ 1

Author(s):

Hector Basoalto ◽

Paul L. Blackwell

Keyword(s):

Grain Boundary ◽

Strain Rate ◽

Strain Rate Sensitivity ◽

Rate Sensitivity ◽

Grain Boundary Sliding ◽

Dislocation Slip ◽

Microstructural Parameters ◽

Sliding Mechanism ◽

Physically Based ◽

Boundary Sliding

The conventional consensus has it that the magnitude of the strain rate sensitivity observed in superplastic materials is linked with grain boundary sliding. The grain boundary sliding mechanism is thought to theoretically produce a strain rate sensitivity exponent of 0.5, which is in good agreement with experimental data. The present paper argues that a rate sensitivity of 0.5 can be generated by dislocation slip under certain temperature and strain rate regimes that overlap with conditions representative of superplasticity. A physically based slip model that links the relevant microstructural parameters to the macroscopic strain rate is proposed.

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Texture Change during Superplastic Deformation in Fine-Grained Magnesium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.838-839.59 ◽

2016 ◽

Vol 838-839 ◽

pp. 59-65 ◽

Cited By ~ 2

Author(s):

Hiroyuki Watanabe ◽

Tokuteru Uesugi ◽

Yorinobu Takigawa ◽

Kenji Higashi

Keyword(s):

Grain Boundary ◽

Magnesium Alloys ◽

Superplastic Deformation ◽

Longitudinal Direction ◽

Grain Boundary Sliding ◽

Dislocation Slip ◽

Grain Rotation ◽

Fine Grained ◽

Texture Change ◽

Boundary Sliding

Texture change during superplastic deformation was examined and compared in two magnesium alloys with different chemical composition. These alloys were extruded to refine the microstructure. The pre-existing basal texture of both alloys became slightly more random within the bulk probably owing to grain boundary sliding and the accompanying grain rotation. However, the texture changes differed between tensile and compressive deformation along the extrusion (longitudinal) direction. This fact suggests that dislocation slip is important in superplastic deformation. It was concluded that dislocation slip acts primarily as an accommodation mechanism for grain boundary sliding.

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Superplasticity in NiAl and NiAl-based alloys

Journal of Materials Research ◽

10.1557/jmr.2002.0344 ◽

2002 ◽

Vol 17 (9) ◽

pp. 2346-2356 ◽

Cited By ~ 6

Author(s):

J. J. Guo ◽

X. X. Du ◽

L. L. Zhou ◽

B. D. Zhou ◽

Y. Y. Qi ◽

...

Keyword(s):

Grain Boundary ◽

Dynamic Recovery ◽

Columnar Structure ◽

Grain Boundary Sliding ◽

Dislocation Slip ◽

Directionally Solidified ◽

Superplastic Behavior ◽

Fine Grained ◽

Fine Grained Structure ◽

Boundary Sliding

Superplastic deformation was realized on NiAl and NiAl-based alloys prepared by both common casting and directional solidification. Directionally solidified NiAl–27Fe–3Nb alloy as well as conventionally cast NiAl, NiAl–25Cr, NiAl–9Mo, NiAl–20Fe–Y.Ce, and NiAl–30Fe–Y alloys exhibited typical deformation characteristics shown in conventionally superplastic materials. NiAl and NiAl-based alloys could be divided into three categories depending on their different superplastic behavior: finely grained structure (NiAl–9Mo, NiAl–25Cr, NiAl–20.4Fe–Y.Ce, NiAl–30Fe–Y), coarsely grained structure (NiAl), and columnar structure (NiAl–27Fe–3Nb). The corresponding deformation mechanisms for fine-grained structure, coarsely grained structure, and columnar structure were grain boundary sliding or grain boundary sliding accompanied by dynamic recrystallization, dynamic recovery and recrystallization, and intragrain dislocation slip, respectively.

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Examination of Fracture Interfaces in Silicon Nitride

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113925 ◽

1975 ◽

Vol 33 ◽

pp. 60-61

Author(s):

Nancy J. Tighe

Keyword(s):

Silicon Nitride ◽

Grain Boundary ◽

Crack Growth ◽

Subcritical Crack Growth ◽

Slow Crack Growth ◽

Ceramic Materials ◽

Grain Boundary Sliding ◽

Boundary Phase ◽

Turbine Engines ◽

Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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