Enhanced strain-rate sensitivity in fcc nanocrystals due to grain-boundary diffusion and sliding

2008 ◽  
Vol 56 (8) ◽  
pp. 1741-1752 ◽  
Author(s):  
Yujie Wei ◽  
Allan F. Bower ◽  
Huajian Gao
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Diffusion ◽  
Enhanced Strain

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

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.

Slip Induced Strain Rate Sensitivity for Superplastic Material?

2012 ◽  
Vol 735 ◽  
pp. 31-36 ◽  
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.

Strain-Rate Sensitivity Enhanced by Grain-Boundary Sliding in Creep Condition for AZ31 Magnesium Alloy at Room Temperature

2016 ◽  
Vol 838-839 ◽  
pp. 106-109 ◽  
Author(s):  
Tetsuya Matsunaga ◽  
Hidetoshi Somekawa ◽  
Hiromichi Hongo ◽  
Masaaki Tabuchi
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
High Strain ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
High Strain Rates ◽  
Boundary Sliding

This study investigated strain-rate sensitivity (SRS) in an as-extruded AZ31 magnesium (Mg) alloy with grain size of about 10 mm. Although the alloy shows negligible SRS at strain rates of >10-5 s-1 at room temperature, the exponent increased by one order from 0.008 to 0.06 with decrease of the strain rate down to 10-8 s-1. The activation volume (V) was evaluated as approximately 100b3 at high strain rates and as about 15b3 at low strain rates (where b is the Burgers vector). In addition, deformation twin was observed only at high strain rates. Because the twin nucleates at the grain boundary, stress concentration is necessary to be accommodated by dislocation absorption into the grain boundary at low strain rates. Extrinsic grain boundary dislocations move and engender grain boundary sliding (GBS) with low thermal assistance. Therefore, GBS enhances and engenders SRS in AZ31 Mg alloy at room temperature.

Cohesive Zone Model for Crack Propagation in a Viscoplastic Polycrystal Material at Elevated Temperature

2006 ◽  
Vol 306-308 ◽  
pp. 187-192
Author(s):  
Yan Qing Wu ◽  
Hui Ji Shi
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Matrix Material ◽  
Rate Sensitivity ◽  
Zone Model ◽  
Dissipation Energy ◽  
Plastic Dissipation

This study looks at the crack propagation characteristics based on the cohesive zone model (CZM), which is implemented as a user defined element within FE system ABAQUS. A planar crystal model is applied to the polycrystalline material at elevated temperature in which grain boundary regions are included. From the point of energy, interactions between the cohesive fracture process zones and matrix material are studied. It’s shown that the material parameter such as strain rate sensitivity of grain interior and grain boundary strongly influences the plastic and cohesive energy dissipation mechanisms. The higher the strain rate sensitivity is, the larger amount of the external work will be transformed into plastic dissipation energy than into cohesive energy which could delay the rupturing of cohesive zone. By comparisons, when strain rate sensitivity decreases, plastic dissipation energy is reduced and the cohesive dissipation energy increases. In this case, the cohesive zones fracture more quickly. In addition to the matrix material parameter, influence of cohesive strength and critical displacement in CZM on stress triaxiality at grain interior and grain boundary regions are also investigated. It’s shown that enhancing cohesive zones ductility could improve matrix materials resistance to void damage.

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

2010 ◽  
Vol 667-669 ◽  
pp. 677-682 ◽  
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.

Strain rate sensitivity of Cu/Ta multilayered films: Comparison between grain boundary and heterophase interface

2016 ◽  
Vol 111 ◽  
pp. 123-126 ◽  
Author(s):  
Q. Zhou ◽  
J.J. Li ◽  
F. Wang ◽  
P. Huang ◽  
K.W. Xu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Multilayered Films

Strain Rate Sensitivity of a Nanocrystalline Cu–Ni–P Alloy

2005 ◽  
Vol 20 (11) ◽  
pp. 2955-2959 ◽  
Author(s):  
J. Chen ◽  
Y.N. Shi ◽  
K. Lu
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Nanoindentation Technique ◽  
Pure Cu

Nanoindentation technique was used to measure the strain rate sensitivity (m) of a nanocrystalline Cu-Ni-P alloy prepared by means of electrodeposition. The m value decreases from 0.034 to 0.018 when the nominal grain size increases from 7 nm to 33 nm. Both m values of the alloy are obviously lower than those of the pure Cu with similar grain size, implying that P segregation at grain boundaries might play a key role in retarding grain boundary activities as compared to pure Cu samples.

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