Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.915 ◽

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%.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.607 ◽

2010 ◽

Vol 654-656 ◽

pp. 607-610 ◽

Cited By ~ 6

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.

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Special Effects in Deformation Mechanism Maps for Austenitic Stainless Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.869.543 ◽

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.

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Syn-shearing deformation mechanisms of minerals in partially molten metapelites

10.31223/x54k9x ◽

2021 ◽

Author(s):

Dripta Dutta ◽

Santanu Misra ◽

David Mainprice

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Grain Boundary Sliding ◽

Cylindrical Sample ◽

Deformation Mechanisms ◽

Axial Section ◽

Fine Grain ◽

Shearing Deformation ◽

Boundary Sliding ◽

Quartz Grains

We investigated an experimentally sheared (γ = 15, γ ̇ = 3 x 10-4s-1, 300 MPa, 750°C) quartz-muscovite aggregate to understand the deformation of parent and new crystals in partially molten rocks. The SEM and EBSD analyses along the longitudinal axial section of the cylindrical sample suggest that quartz and muscovite melted partially and later produced K-feldspar, ilmenite, biotite, mullite, and cordierite. Quartz grains became finer, and muscovite was almost entirely consumed in the process. With increasing , melt and crystal fractions decreased and increased, respectively. Amongst the new minerals, K-feldspar grains (highest area fraction and coarsest) nucleated first, whereas cordierite and mullite grains, finest and least in number, respectively, nucleated last. Fine grain size, weak CPOs, low intragranular deformation, and equant shapes suggest both initial and new minerals deformed dominantly by melt-assisted grain boundary sliding, which is further substantiated by higher misorientations between adjacent grains of quartz, K-feldspar, and ilmenite.

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Combined AFM, SEM and crystal plasticity analysis of grain boundary sliding in titanium at room temperature

Mechanics of Materials ◽

10.1016/j.mechmat.2016.09.001 ◽

2016 ◽

Vol 103 ◽

pp. 18-27 ◽

Cited By ~ 13

Author(s):

V. Doquet ◽

B. Barkia

Keyword(s):

Grain Boundary ◽

Crystal Plasticity ◽

Room Temperature ◽

Grain Boundary Sliding ◽

Boundary Sliding

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Is Superplasticity in the Future of Nanophase Materials?

MRS Proceedings ◽

10.1557/proc-196-59 ◽

1990 ◽

Vol 196 ◽

Cited By ~ 13

Author(s):

R. W. Siegel

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Room Temperature ◽

Grain Boundary Sliding ◽

Atomic Clusters ◽

Diffusional Creep ◽

Ultrafine Grain ◽

Grain Sizes ◽

Nanophase Materials ◽

Boundary Sliding

ABSTRACTThe ultrafine grain sizes and high diffusivities in nanophase materials assembled from atomic clusters suggest that these materials may have a strong tendency toward superplastic mechanical behavior. Both small grain size and enhanced diffusivity can be expected to lead to increased diffusional creep rates as well as to a significantly greater propensity for grain boundary sliding. Recent mechanical properties measurements at room temperature on nanophase Cu, Pd, and TiO2, however, give no indications of superplasticity. Nonetheless, significant ductility has been clearly demonstrated in these studies of both nanophase ceramics and metals. The synthesis of cluster-assembled nanophase materials is described and the salient features of what is known of their structure and mechanical properties is reviewed. Finally, the answer to the question posed in the title is addressed.

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The role of grain size evolution in the rheology of ice: implications for reconciling laboratory creep data and the Glen flow law

The Cryosphere ◽

10.5194/tc-15-4589-2021 ◽

2021 ◽

Vol 15 (9) ◽

pp. 4589-4605

Author(s):

Mark D. Behn ◽

David L. Goldsby ◽

Greg Hirth

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Stress Exponent ◽

Ice Sheets ◽

Grain Boundary Sliding ◽

Dislocation Creep ◽

Ice Flow ◽

Size Evolution ◽

Boundary Sliding ◽

Flow Law

Abstract. Viscous flow in ice is often described by the Glen flow law – a non-Newtonian, power-law relationship between stress and strain rate with a stress exponent n ∼ 3. The Glen law is attributed to grain-size-insensitive dislocation creep; however, laboratory and field studies demonstrate that deformation in ice can be strongly dependent on grain size. This has led to the hypothesis that at sufficiently low stresses, ice flow is controlled by grain boundary sliding, which explicitly incorporates the grain size dependence of ice rheology. Experimental studies find that neither dislocation creep (n ∼ 4) nor grain boundary sliding (n ∼ 1.8) have stress exponents that match the value of n ∼ 3 in the Glen law. Thus, although the Glen law provides an approximate description of ice flow in glaciers and ice sheets, its functional form is not explained by a single deformation mechanism. Here we seek to understand the origin of the n ∼ 3 dependence of the Glen law by using the “wattmeter” to model grain size evolution in ice. The wattmeter posits that grain size is controlled by a balance between the mechanical work required for grain growth and dynamic grain size reduction. Using the wattmeter, we calculate grain size evolution in two end-member cases: (1) a 1-D shear zone and (2) as a function of depth within an ice sheet. Calculated grain sizes match both laboratory data and ice core observations for the interior of ice sheets. Finally, we show that variations in grain size with deformation conditions result in an effective stress exponent intermediate between grain boundary sliding and dislocation creep, which is consistent with a value of n = 3 ± 0.5 over the range of strain rates found in most natural systems.

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Research on Micro-Mechanism of Nanocomposite Ceramic in Two-Dimensional Ultrasound Grinding

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.359-360.344 ◽

2007 ◽

Vol 359-360 ◽

pp. 344-348 ◽

Cited By ~ 5

Author(s):

Bo Zhao ◽

Yan Wu ◽

Guo Fu Gao ◽

Feng Jiao

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Deformation Mechanism ◽

Ground Surface ◽

Grain Boundary Sliding ◽

Second Phase ◽

Two Dimensional ◽

Composite Ceramics ◽

Nano Composite ◽

Boundary Sliding

Surface microstructure of nano-composite ceramics prepared by mixed coherence system and machined by two-dimensional ultrasonic precision grinding was researched using TEM, SEM, XRD detector and other equipments. Structure, formation mechanism and characteristic of metamorphic layer of ground surface of nano-composite ceramics were researched. The experiment shows micro deformation mechanism of ceramic material in two-dimensional ultrasound grinding is twin grain boundary and grain-boundary sliding for Al2O3, and it is crystal dislocation of enhanced phase, matrix grain boundary sliding, coordination deformation of intergranular second phase as well as its deformation mechanism for nano-composite ceramics. The fracture surfaces of nano-composite materials with different microscopic structure were observed using TEM and SEM. Research shows that ZrO2 plays an important influence on the generation and expansion of crack, and enhances the strength of grain boundaries. When grain boundaries is rich in the ZrO2 particles, the crack produced in grinding process will be prevented, and the surface with plastic deformation will be smooth. The results shows nanoparticles dispersed in grain boundary prevents crack propagation and makes materials fracture transgranularly which makes the processed surface fine.

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