First Direct In Situ Observation of Grain Boundary Sliding in Ultrafine Grained Noble Metal

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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The Role of Diffusion Accommodation and Phase Boundary Wetting in the Deformation Behaviour of Ultrafine Grained Sn-Pb Eutectic

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.297-301.1002 ◽

2010 ◽

Vol 297-301 ◽

pp. 1002-1009 ◽

Cited By ~ 1

Author(s):

Faina Muktepavela ◽

R. Zabels

Keyword(s):

Grain Boundary ◽

Diffusion Processes ◽

Deformation Behaviour ◽

Grain Boundary Sliding ◽

Ultrafine Grained ◽

Interphase Boundaries ◽

Boundary Sliding ◽

High Homologous Temperature ◽

Microscopy Techniques

Mechanical properties, microstructure of the Sn–38wt. %Pb eutectic and the development of deformation - induced diffusion processes on interphase boundaries (IB) were investigated. Experiments were carried out both in deformed and annealed states of eutectic using micro- and nanoindentation, SEM, AFM and optical microscopy techniques. It was found that the deformation of the annealed alloy is localized at the Pb/Sn interphase boundaries and occurs by grain boundary sliding (GBS) accompanied by sintering micropore processes under the action of the capillary forces on the Pb/Sn IB. During severe plastic deformation of Sn-Pb eutectic phase transition in the Sn grain boundary occurs. This deformation-induced process takes place due to the wetting of tin with Pb. These diffusion accommodation processes (sintering and wetting) are facilitated by the low values of the Pb/Sn interphase energy (0.07 J/m2). Wetting is thermodynamically favourable because the condition γgb > 2 γib is satisfied and it is also kinetically allowed due to the relatively high homologous temperature (> 0.5•Tm). The obtained values of the nanohardness and elastic modulus evidence that the IBs in the Sn–Pb eutectic have to be considered as a separate quasi-phase with its own properties.

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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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Tribological Behavior of Mg-Mg2Si In Situ Composite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.710.401 ◽

2012 ◽

Vol 710 ◽

pp. 401-406

Author(s):

Kumaraswamy Kaliamma Ajith Kumar ◽

Uma Thanu Subramonia Pillai ◽

Bellambettu Chandrasekhara Pai ◽

Madhusudan Chakraborty

Keyword(s):

Elevated Temperature ◽

Wear Rate ◽

Grain Boundary ◽

Tribological Behavior ◽

Grain Boundary Sliding ◽

Dry Sliding ◽

Boundary Sliding ◽

Si Content ◽

State Processing

Mg-Mg2Si in-situ composites by the addition of Si in Mg have become more attractive since the Mg2Si phase impedes the grain boundary sliding at elevated temperature because of its inherent properties which greatly improve the heat and wear resistances. In the present work, Mg-Mg2Si composites have been prepared by the liquid state processing with different amount of silicon additions. The microstructure and dry sliding tribological behavior of the composites have been studied. SEM studies reveal the wear mechanisms involved in these composites. The results indicate that wear rate of the composites is a function of Mg2Si content in the composite. The effect of Mg2Si morphology and distribution on the overall mechanism is also discussed.

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The Effect of Grain Boundary Sliding and Strain Rate Sensitivity on the Ductility of Ultrafine-Grained Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.677 ◽

2010 ◽

Vol 667-669 ◽

pp. 677-682 ◽

Cited By ~ 11

Author(s):

Nguyen Q. Chinh ◽

Tamás Csanádi ◽

Jenő Gubicza ◽

Ruslan Valiev ◽

Boris Straumal ◽

...

Keyword(s):

Grain Boundary ◽

Strain Rate ◽

Strain Rate Sensitivity ◽

Rate Sensitivity ◽

Grain Boundary Sliding ◽

Room Temperature Ductility ◽

Ultrafine Grained ◽

Boundary Sliding ◽

Ultrafine Grained Materials ◽

High Strain Rate Sensitivity

Most ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) exibit only limited ductility which is correlated with the low strain rate sensitivity (SRS) of these materials. Recently, it was demonstrated that SPD is capable of increasing the room temperature ductility of aluminum-based alloys attaining elongations up to 150%, together with relatively high strain rate sensitivity. In the present work, additional results and discussions are presented on the effect of grain boundary sliding (GBS) and SRS on the ductility of some UFG metals and alloys. The characteristics of constitutive equations describing the steady-state deformation process are quantitatively analyzed for a better understanding of the effects of grain boundaries and strain rate sensitivity.

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Cooperative grain boundary sliding and nanograin nucleation process in nanocrystalline, ultrafine-grained, and polycrystalline solids

Physical Review B ◽

10.1103/physrevb.84.094103 ◽

2011 ◽

Vol 84 (9) ◽

Cited By ~ 20

Author(s):

S. V. Bobylev ◽

N. F. Morozov ◽

I. A. Ovid’ko

Keyword(s):

Grain Boundary ◽

Grain Boundary Sliding ◽

Nucleation Process ◽

Ultrafine Grained ◽

Boundary Sliding ◽

Polycrystalline Solids

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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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