Competing deformation mechanisms in nanocrystalline metals and alloys: Coupled motion versus grain boundary sliding

2012 ◽  
Vol 60 (17) ◽  
pp. 6076-6085 ◽  
Author(s):  
Jonathan Schäfer ◽  
Karsten Albe
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Metals And Alloys ◽  
Deformation Mechanisms ◽  
Nanocrystalline Metals ◽  
Coupled Motion ◽  
Boundary Sliding ◽  
Motion Versus

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

2010 ◽  
Vol 667-669 ◽  
pp. 915-920
Author(s):  
Konstantin Ivanov ◽  
Evgeny V. Naydenkin
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Structure Evolution ◽  
Dislocation Slip ◽  
Polished Surface ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Boundary Sliding

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%.

Temperature Dependence of Compressive Deformation Behavior of Mg89Zn4Y7 Extruded LPSO-Phase Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 607-610 ◽  
Author(s):  
Koji Hagihara ◽  
Akihito Kinoshita ◽  
Yuya Sugino ◽  
Michiaki Yamasaki ◽  
Yoshihito Kawamura ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Petch Relationship ◽  
Lpso Phase ◽  
Boundary Sliding

Deformation mechanisms of Mg89Zn4Y7 (at.%) extruded alloy, which is mostly composed of LPSO-phase, was investigated focusing on their temperature dependence. The yield stress of as-extruded alloy showed extremely high value of ~480 MPa at RT, but it largely decreased to ~130 MPa at 300 °C. The decreasing rate of the yield stress could be significantly reduced, however, by the annealing of specimen at 400 °C, by suppressing the microyielding which is considered to occur related by the grain boundary sliding in restricted regions. The yield stress of the annealed specimens with random textures could be estimated by the Hall-Petch relationship by regarding the length of long-axis of plate-like grains as a grain size between RT and 300 °C. The yield stress of the annealed specimens maintained high values even at 200°C, but it also showed large decreases at 300 °C.

scholarly journals Syn-kinematic hydration reactions, dissolution-precipitation creep and grain boundary sliding in experimentally deformed plagioclase-pyroxene mixtures

2018 ◽  
Author(s):  
Sina Marti ◽  
Holger Stünitz ◽  
Renée Heilbronner ◽  
Oliver Plümper ◽  
Rüdiger Kilian
Keyword(s):  
Grain Boundary ◽  
Confining Pressure ◽  
Shear Zones ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Dislocation Creep ◽  
Crystallographic Preferred Orientation ◽  
Mafic Rocks ◽  
Boundary Sliding ◽  
Crustal Shear Zones

Abstract. While it is widely observed that mafic rocks are able to exeprience high strains by viscous flow, details on their rheology and deformation mechanisms are poorly constrained. Here, rock deformation experiments on four different, water-added plagioclase-pyroxene mixtures are presented: (i) plagioclase(An60-70) – clinopyroxene – orthopyroxene, (ii) plagioclase(An60) – diopside, (iii) plagioclase(An60) – enstatite and (iv) plagioclase(An01) – enstatite. Samples were deformed in general shear at strain rates of 3 × 10−5 to 3 × 10−6 s−1, 800 °C and confining pressure of 1.0 or 1.5 GPa. Results indicate that dissolution-precipitation creep (DPC) and grain boundary sliding (GBS) are the dominant deformation mechanisms. Coinciding with sample deformation, syn-kinematic mineral reactions yield abundant nucleation of new grains; the resulting intense grain size reduction is considered crucial for the activity of DPC and GBS. In high strain zones dominated by plagioclase, a weak, non-random and geometrically consistent crystallographic preferred orientation (CPO) is observed. Usually, a CPO is considered a consequence of dislocation creep, but the experiments presented here demonstrate that a CPO can develop during DPC and GBS. This study provides new evidence for the importance of DPC and GBS in mid-crustal shear zones within mafic rocks, which has important implications on understanding and modelling of mid-crustal rheology and flow.

Special Effects in Deformation Mechanism Maps for Austenitic Stainless Steels

2016 ◽  
Vol 869 ◽  
pp. 543-549
Author(s):  
Sergio Neves Monteiro ◽  
Frederico Muylaert Margem ◽  
Lucas Tedesco Bolzan ◽  
George Lobo Nobre Fernandes ◽  
Verônica Scarpini Cândido
Keyword(s):  
Grain Boundary ◽  
Stainless Steels ◽  
Deformation Mechanism ◽  
Austenitic Stainless Steels ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Engineering Systems ◽  
Special Effects ◽  
Operational Life ◽  
Boundary Sliding

The domains of the existence of deformation mechanisms in a map associated with phase transformation and mechanical effects related to aging processes were investigated in austenitic stainless steels. It was also discussed the participation of grain boundary sliding, both as an additional deformation mechanism and a damage accumulation process. A prediction analysis for two typical high temperature engineering systems was attempted based on the map information. This prediction indicates the possibility of grain boundary sliding and creep strain jumps to interfere with the expected operational life of components in these systems operating at high temperatures.

Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys

2004 ◽  
Vol 449-452 ◽  
pp. 665-668 ◽  
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.

Superplastic Deformation Mechanisms in High Magnesium Contenting Aluminum Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 66-71 ◽  
Author(s):  
O.A. Yakovtseva ◽  
Anastasia V. Mikhaylovskaya ◽  
A.G. Mochugovskiy ◽  
V.V. Cheverikin ◽  
Vladimir K. Portnoy
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Superplastic Deformation ◽  
Effective Activation Energy ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Effective Activation ◽  
Continuous Formation ◽  
Boundary Sliding ◽  
Dynamic Grain Growth

The evolution of surface, grains and dislocation structures during superplastic deformation was studied in Al–6.8%Mg–0.6%Mn–0.25%Cr alloy by SEM, EBSD, TEM techniques. The effective activation energy of superplastic deformation was calculated. Contribution of grain boundary sliding was defined during superplastic deformation. Low value of grain boundary sliding, significant dynamic grain growth in stress direction, high dislocations activity and permanent continuous formation of sub-grain boundaries during superplastic deformation were found.

Mechanisms-based constitutive equations for the superplastic behaviour of a titanium alloy

1996 ◽  
Vol 31 (3) ◽  
pp. 187-196 ◽  
Author(s):  
M Zhou ◽  
F P E Dunne
Keyword(s):  
Titanium Alloy ◽  
Grain Boundary ◽  
Grain Growth ◽  
Constitutive Equations ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Diffusional Creep ◽  
Dislocation Creep ◽  
Boundary Sliding

Mechanisms-based constitutive equations are proposed for the high-temperature behaviour of a class of titanium alloys, for which the deformation mechanisms include diffusional creep, grain boundary sliding, dislocation creep and grain growth. A computational procedure has been developed for the determination of the constitutive equations from a material database. The constitutive equations and the procedure for their determination have been validated by modelling the behaviour of the titanium alloy Ti-6Al-4V at 927°C. It is shown that the procedure developed for the determination of the mechanisms-based constitutive equations can be used to identify the important deformation mechanisms in operation for particular stress, temperature and strain rate conditions. For the case of the Ti-6Al-4V material, the procedure developed correctly predicts the material hardening due to grain growth and indicates that an additional hardening mechanism operates. In addition, the procedure is able to identify grain boundary sliding as a predominant deformation mechanism. The constitutive equations, which are generic in nature, and the procedure for their determination are applicable over a range of materials and are suitable for modelling the macroscopic and the important microscopic aspects of material behaviour during processing. The equations may be readily determined using the procedure presented, which is highly suitable for development as an expert system, to completely automate the process.

Asymmetric extensional structures and their implications for the generation of melanges

1987 ◽  
Vol 124 (4) ◽  
pp. 311-318 ◽  
Author(s):  
D. T. Needham
Keyword(s):  
Grain Boundary ◽  
Shear Bands ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Metamorphic Rocks ◽  
Southwest Japan ◽  
Boundary Sliding ◽  
Shimanto Belt ◽  
Pressure Controlled ◽  
Extensional Structures

AbstractStudies of melanges in the Shimanto Belt of southwest Japan have shown that many of the included blocks exhibit asymmetric geometries, similar to boudins and inclusions in medium grade metamorphic rocks which have been subjected to markedly non-coaxial strains. Deformation is accomplished by mesoscopically ductile processes such as pore-pressure-controlled or diffusionally-controlled grain boundary sliding, although localized fracture and cataclasis also occurs. It is suggested that the melanges developed by the propagation of extensional displacement zones, analogous to shear bands, through sandstone beds, so progressively dismembering them. Studies of the detailed internal geometries of melanges along with the deformation mechanisms active during their formation may help resolve the mode of formation of these problematic units.

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