Origin of the twinning to slip transition with grain size refinement, with decreasing strain rate and with increasing temperature in magnesium

2015 ◽  
Vol 88 ◽  
pp. 232-244 ◽  
Author(s):  
C.M. Cepeda-Jiménez ◽  
J.M. Molina-Aldareguia ◽  
M.T. Pérez-Prado
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Size Refinement ◽  
Increasing Temperature ◽  
Slip Transition

Microstructural Design for Attaining High-Strain-Rate Superplasticity in Oxide Materials

2006 ◽  
Vol 45 ◽  
pp. 923-932
Author(s):  
Keijiro Hiraga ◽  
Byung Nam Kim ◽  
Koji Morita ◽  
Tohru Suzuki ◽  
Yoshio Sakka
Keyword(s):  
Grain Size ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Spinel Phase ◽  
Tetragonal Zirconia ◽  
Secondary Phases ◽  
Cavitation Damage ◽  
Size Refinement ◽  
Dynamic Grain Growth

Factors limiting the strain rate of superplastic deformation in oxide ceramics are discussed from existing knowledge about the mechanisms of high-temperature plastic deformation and intergranular cavitation. The discussion leads to the following guide: simultaneously controlling the initial grain size, diffusivity, dynamic grain growth, homogeneity of microstructure and the number of residual defects is essential to attain high-strain-rate superplasticity. Along this guide, high-strain-rate superplasticity (HSRS) is attainable in some oxides consisting of tetragonal zirconia, α-alumina and a spinel phase: tensile ductility reached 300-2500% at a strain rate of 0.01-1.0 s-1. Post-deformation microstructure indicates that some secondary phases may suppress cavitation damage and thereby enhance HSRS. The guide is also essential to lower the limit of deformation temperature for a given strain rate. In monolithic tetragonal zirconia, grain-size refinement combined with doping of aliovalnt cations such as Mg2+, Ti4+ and Al3+ led to HSRS at 1350 °C.

Deformation behavior and strain rate sensitivity of nanostructured materials at moderate temperatures

2005 ◽  
Vol 880 ◽  
Author(s):  
Cécilie Duhamel ◽  
Sandrine Guérin ◽  
Martin Hÿtch ◽  
Yannick Champion
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Nanostructured Materials ◽  
Strain Rate Sensitivity ◽  
Deformation Behavior ◽  
Rate Sensitivity ◽  
Nanocrystalline Copper ◽  
Fcc Metals ◽  
Thermally Activated ◽  
Increasing Temperature

AbstractStrain-rate jump tests in compression are carried out on nanostructured copper (grain size = 90 nm) at moderate temperatures (353K - 393K). Strain-rate sensitivity m is measured as a function of temperature, T, and strain rate, έ. Increasing temperature or decreasing strain rate induces an increase in the strain-rate sensitivity. For (έ, T) = (1×10-5 s-1, 393K), m is equal to 0.17 which is the highest value reported for nanocrystalline copper. These results of enhanced m are encouraging in terms of gain in ductility. The measurements emphasize the existence of a thermally activated mechanism different from the normal rate-controlling process observed for microcrystalline fcc metals.

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

2018 ◽  
Vol 385 ◽  
pp. 27-32
Author(s):  
K. Anantha Padmanabhan ◽  
S. Balasivanandha Prabu ◽  
A. Arsath Abbas Ali
Keyword(s):  
Grain Size ◽  
Steady State ◽  
Strain Rate ◽  
Linear Function ◽  
Power Law ◽  
Controlling Mechanism ◽  
Different Temperatures ◽  
Pi Theorem ◽  
High Homologous Temperature ◽  
Increasing Temperature

“Power law’’ representation is used to describe minimum creep rate and “steady state” superplastic deformation. In creep isothermal log stress – log strain rate relationship is linear for so long as the rate controlling mechanism remains unchanged. During optimal superplastic flow the slope of this curve changes even when there is no change in the rate controlling mechanism, i.e. the stress exponent, n, at a constant temperature and grain size is a function of strain rate. For a constant rate controlling mechanism, in both the phenomena, n decreases with increasing temperature. Grain size has no effect on creep, but its effect is significant in superplasticity. Therefore, analyzing creep and superplasticity data by treating n for any given mechanism as a constant independent of stress and temperature is questionable. In this analysis stress is normalized with respect to a reference stress, rather than the shear modulus. The microstructure dependence comes through the Buckingham Pi theorem. When contribution from microstructure terms to isothermal strain rate is constant, Laurent’s theorem helps generate a set of values for n. It is shown that the simplest solution, viz. n is independent of stress, but is a linear function of temperature, describes steady state creep. (The case n is independent of both stress and temperature follows as a special case.) The second simplest solution, viz. n is a linear function of both temperature and stress corresponds to steady state superplasticity. Using the equations, the values of n, activation energies for the rate controlling processes and strain rates at different temperatures and stresses could be estimated for both creep and superplasticity. The analysis is validated using experimental results concerning many systems. iiThis lecture is dedicated to the sacred memory of late Prof. Oleg D. Sherby.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

Effect of Grain Size on Deformation Twinning Behavior of Ti6Al4V Alloy

2015 ◽  
Vol 830-831 ◽  
pp. 337-340
Author(s):  
Ashish Kumar Saxena ◽  
Manikanta Anupoju ◽  
Asim Tewari ◽  
Prita Pant
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Deformation Behaviour ◽  
Air Cooling ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Β Phase ◽  
Plastic Deformation Behavior

An understanding of the plastic deformation behavior of Ti6Al4V (Ti64) is of great interest because it is used in aerospace applications due to its high specific strength. In addition, Ti alloys have limited slip systems due to hexagonal crystal structure; hence twinning plays an important role in plastic deformation. The present work focuses upon the grain size effect on plastic deformation behaviour of Ti64. Various microstructures with different grain size were developed via annealing of Ti64 alloy in α-β phase regime (825°C and 850°C) for 4 hours followed by air cooling. The deformation behavior of these samples was investigated at various deformation temperature and strain rate conditions. Detailed microstructure studies showed that (i) smaller grains undergoes twinning only at low temperature and high strain rate, (ii) large grain samples undergo twinning at all temperatures & strain rates, though the extent of twinning varied.

Grain-Size Refinement in Al-Mn-Ce Rapidly-Quenched Alloys

2000 ◽  
Vol 343-346 ◽  
pp. 27-32
Author(s):  
R. Nicula ◽  
Adrian Jianu ◽  
G. Holzhüter ◽  
T. Barfels ◽  
E. Burkel
Keyword(s):  
Grain Size ◽  
Size Refinement ◽  
Rapidly Quenched Alloys

Grain size refinement, texture analysis and effect on the tensile properties of a novel Inconel 718

2021 ◽  
Vol 292 ◽  
pp. 129633
Author(s):  
Ramkumar Thulasiram ◽  
Selvakumar Mani ◽  
Narayanan Ramaswamy ◽  
Mohanraj Murugesan
Keyword(s):  
Grain Size ◽  
Tensile Properties ◽  
Texture Analysis ◽  
Inconel 718 ◽  
Size Refinement

Superplastic Behavior of a Cu-Cr-Zr Alloy Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 404-409
Author(s):  
Roman Mishnev ◽  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Strain Rate ◽  
Temperature Interval ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Average Grain Size ◽  
Gauge Section ◽  
Zr Alloy

A Cu-0.87%Cr-0.06%Zr alloy was subjected to equal channel angular pressing (ECAP) at a temperature of 400 °C up to a total strain of ~ 12. This processing produced ultra-fine grained (UFG) structure with an average grain size of 0.6 μm and an average dislocation density of ~4×1014 m-2. Tensile tests were carried out in the temperature interval 450 – 650 °C at strain rates ranging from 2.8´10-4 to 0.55 s-1. The alloy exhibits superplastic behavior in the temperature interval 550 – 600 °C at strain rate over 5.5´10-3 s-1. The highest elongation-to-failure of ~300% was obtained at a temperature of 575 °C and a strain rate of 2.8´10-3 s-1 with the corresponding strain rate sensitivity of 0.32. It was shown the superplastic flow at the optimum conditions leads to limited grain growth in the gauge section. The grain size increases from 0.6 μm to 0.87 μm after testing, while dislocation density decreases insignificantly to ~1014 m-2.

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