Mesoscopic Scale Modeling of "Superplastic" Flow in Geological and Glacial Materials

M. Ravithul Basariya; K. Anantha Padmanabhan

doi:10.4028/www.scientific.net/DDF.385.33

Paper Titles

Superplastic Flow and Micro-Mechanical Response of Ultrafine-Grained Materials
p.9

Superplasticity of Friction-Stir Welds of Zr-Modified 5083 Aluminum Alloy with Ultrafine-Grained Structure
p.15

Mechanical Behavior of Twinning Induced Plasticity Steel Processed by Warm Forging and Annealing
p.21

On the Nuances in the Power Law Description and Interpretation of High Homologous Temperature Creep and Superplasticity Data
p.27

Mesoscopic Scale Modeling of "Superplastic" Flow in Geological and Glacial Materials
p.33

Superplasticity of Aerospace 7075 (Al-Zn-Mg-Cu) Aluminium Alloy Obtained by Severe Plastic Deformation
p.39

Arrhenius-Type Constitutive Equation Model of Superplastic Deformation Behaviour of Different Titanium Based Alloys
p.45

Effect of Ultrasonic Treatment on the Characteristics of Superplasticity of Titanium Alloy Ti-6Al-4V
p.53

Low Temperature Superplasticity in Ultrafine-Grained AZ31 Alloy
p.59

HomeDefect and Diffusion ForumDefect and Diffusion Forum Vol. 385Mesoscopic Scale Modeling of "Superplastic" Flow...

Mesoscopic Scale Modeling of "Superplastic" Flow in Geological and Glacial Materials

Abstract:

A viewpoint that suggests that grain/ interphase boundary sliding (GBS) that develops to a mesoscopic scale (“cooperative boundary sliding”) controls optimal superplastic (SP) deformation is able to explain superplasticity in metals and alloys, ceramics, intermetallics, composites and bulk metallic glasses of grain sizes ranging from a few microns down to a few nanometers. It is extended here to describe grain-size-sensitive (GSS) flow in minerals, rocks and ice within narrow experimental ranges. In this approach the accommodation processes of grain boundary diffusion, dislocation emission from sliding boundaries and/ or grain rotation accompanying boundary sliding are present over extremely short distances and are assumed to be faster than GBS. Analysis shows that GSS creep in geological and glacial materials can be accounted for in terms of four “universal”, mesoscopic scale constants of average values, = 0.197, = 0.415 J.m^-2, = 8.9 and = 0.166, where is the average shear strain associated with a basic boundary sliding event at the level of the atomistics, is the specific grain boundary energy (assumed to be isotropic), is the number of boundaries that align to form a mesoscopic boundary glide plane and “” is a constant that obeys the condition 0<a<0.5, whose magnitude depends on grain shape and size distribution in the material. It is demonstrated that with the help of these four constants and the Frost-Ashby equations for estimating the shear modulus, it is possible to predict steady state GSS creep flow in any geological or glacial material, including those whose mechanical response was not used to obtain the “universal” constants. Whether these observations are evidence for “superplasticity” in these materials can be known only if the findings are reproduced in tensile deformation also.