iMechanica - grain growth
https://imechanica.org/taxonomy/term/899
enCoupled crystal plasticity-probabilistic cellular automata approach to model dynamic recrystallization in magnesium alloys
https://imechanica.org/node/16662
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/899">grain growth</a></div><div class="field-item odd"><a href="/taxonomy/term/5079">texture analysis</a></div><div class="field-item even"><a href="/taxonomy/term/6603">Monter-Carlo simulations</a></div><div class="field-item odd"><a href="/taxonomy/term/9835">DRX</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>
<a href="http://www.sciencedirect.com/science/article/pii/S0749641914000916">http://www.sciencedirect.com/science/article/pii/S0749641914000916</a>
</p>
</div></div></div>Sat, 24 May 2014 11:42:35 +0000ystarase16662 at https://imechanica.orghttps://imechanica.org/node/16662#commentshttps://imechanica.org/crss/node/16662A new model to predict grain nucleation during dynamic recrystallization
https://imechanica.org/node/14887
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/899">grain growth</a></div><div class="field-item odd"><a href="/taxonomy/term/2860">dynamic recrystallization</a></div><div class="field-item even"><a href="/taxonomy/term/4356">nucleation</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><a href="http://www.magnet.ubc.ca/wiki/images/5/5a/Abhijit_Mg2012.pdf">http://www.magnet.ubc.ca/wiki/images/5/5a/Abhijit_Mg2012.pdf</a></p>
<p> </p>
<p>Deformation in metals and alloys is accompanied by high hardening rates and high dislocation </p>
<p>content. Static annealing of deformed metals or forming operations at elevated temperatures can </p>
<p>lead to static and dynamic recrystallization (SRX and DRX). The resultant texture and hence the </p>
<p>properties of such a material are determined by the nucleation and growth of recrystallized grains </p>
<p>conditioned by the deformation. Nucleation in this research is postulated to occur in </p>
<p>regions of the microstructure that have high (locally) stored energy adjacent to a low Nye tensor </p>
<p>(relatively undeformed) zone. </p>
</div></div></div>Sun, 23 Jun 2013 04:55:07 +0000ystarase14887 at https://imechanica.orghttps://imechanica.org/node/14887#commentshttps://imechanica.org/crss/node/14887Post Doctoral Appointment in Thin Film and Grain Growth Modeling
https://imechanica.org/node/12352
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/73">job</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/17">thin film</a></div><div class="field-item odd"><a href="/taxonomy/term/309">evolution of microstructure</a></div><div class="field-item even"><a href="/taxonomy/term/899">grain growth</a></div><div class="field-item odd"><a href="/taxonomy/term/1312">grain-boundary diffusion grain-boundary sliding</a></div><div class="field-item even"><a href="/taxonomy/term/2216">grain boundaries</a></div><div class="field-item odd"><a href="/taxonomy/term/4356">nucleation</a></div><div class="field-item even"><a href="/taxonomy/term/5891">Microstructure characterization</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>Professor Gregory B. Thompson at the University of Alabama seeks post doctoral applicants for thin film and grain growth modeling in metal alloys. The qualified candidate will use modeling to explain and help direct experimental studies. The candidate will primarily focus on understanding how chemical partitioning contributes to stress evolution during physical deposition in metallic films as well as grain growth in metallic alloy systems. The candidate will be able to directly link his/her modeling results to in situ, real time experimentally captured data and advanced analytical microscopy characterization, including atom probe tomography. The post doc should be versed in using molecular dynamics, kinetic monte carlo or related approaches. The candidate will have opportunities to interface and use a variety of state-of-the-art analytical instrumentation in conjunction with his/her modeling centric focus. This will provide for a multi-disciplinary post doctoral research experience. </p>
<p>The post doctoral fellows will be expected to actively publish their research as well as present their research at national and international meetings. The candidates will also assist in proposal writing and preparation. Professor Thompson’s research group collaborates with several national laboratory facilities including Sandia National Laboratories, Oak Ridge National Laboratory, and NASA Glenn Research Center as well as industrial partners. Previous students and post docs in his group have been able to travel and collaborate at these off-site facilities increasing their personal interaction in the field and research education. Successful candidates will be offered competitive stipends and health coverage.</p>
<p>The University of Alabama is located in Tuscaloosa, Alabama, which is approximately 60 miles southwest of Birmingham. The student body is approximately 33,000. Tuscaloosa offers a variety of shopping, restaurants and states parks in the vicinity. The University of Alabama’s College of Engineering was founded in 1831 and is the 5th oldest college of engineering in the country. </p>
<p>Interested applicants are encouraged to contact Professor Thompson:</p>
<p>Dr. Gregory Thompson<br />
University of Alabama<br />
Department of Metallurgical & Materials Engineering <br />
301 7th Ave, 116 Houser Hall <br />
Tuscaloosa, AL 35487-0202 <br />
205-348-1589<br /><a href="http://www.bama.ua.edu/~gthomps/">http://www.bama.ua.edu/~gthomps/</a></p>
</div></div></div>Thu, 26 Apr 2012 15:17:28 +0000gthompson112352 at https://imechanica.orghttps://imechanica.org/node/12352#commentshttps://imechanica.org/crss/node/12352Experimental Observations of Stress-Driven Grain Boundary Migration
https://imechanica.org/node/7272
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/404">Thin Film Mechanical Properties</a></div><div class="field-item odd"><a href="/taxonomy/term/899">grain growth</a></div><div class="field-item even"><a href="/taxonomy/term/1189">nanocrystalline materials</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>
My coworkers (Dan Gianola, Yixiang Gan, and Kevin Hemker) and I have published research results in the December 18th, 2009 issue of Science. In this work, we perform tension tests on specially designed thin film samples to studying the influence of different stress and strain states on mechanically-induced grain growth in nanocrystalline aluminum. Our results indicate that shear stresses drive grain boundaries to move in a manner consistent with recent molecular dynamics simulations and theoretical predictions of coupled grain boundary migration.
</p>
<p>
</p>
<p>
Our paper can be found at:
</p>
<p>
<a href="http://dx.doi.org/10.1126/science.1178226">http://dx.doi.org/10.1126/science.1178226</a>
</p>
<p>
</p>
<p>
<img src="http://gianola.seas.upenn.edu/events/feed_images/Science_image.jpg" border="0" alt="" width="200" /></p>
</div></div></div>Fri, 18 Dec 2009 21:18:34 +0000Tim Rupert7272 at https://imechanica.orghttps://imechanica.org/node/7272#commentshttps://imechanica.org/crss/node/7272Going beyond 2D Neumann-Mullins (or, what is popularly known as, solving the beer froth structure)
https://imechanica.org/node/1302
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/232">coarsening</a></div><div class="field-item odd"><a href="/taxonomy/term/899">grain growth</a></div><div class="field-item even"><a href="/taxonomy/term/900">microstrctural evolution</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>Introduction</span></p>
<p> The <a href="http://dsc.discovery.com/news/2007/04/25/beerfoam_hum.html?category=human&guid=20070425153000" title="Discovery -- beer foam structure solved">blogosphere is abuzz</a> with the latest report of the generalisation of the von Neumann-Mullins grain growth relation to 3 (and N) dimensions by <a href="http://www.math.ias.edu/%7Ephares/macpherson/RDM.html" title="MacPherson homepage">MacPherson</a> and <a href="http://prism.princeton.edu/bios/SrolovitzBio.htm" title="Srolovita homepage">Srolovitz</a> (As an interesting aside, almost all the reports say mathematical structure of beer foam structure resolved, or words to that effect --hence, I also decided to join the bandwagon on that one). I heard Prof. Srolovitz describe the work in a seminar nearly six months ago. Based on my notes of the talk, I would like the explain their work in this post. <a href="http://en.wikipedia.org/wiki/Curvature" title="Curvature wiki">Curvature</a> in the following refers to mean curvature (and not Gaussian).</p>
<p> <span>2D von Neumann-Mullins grain growth relation</span></p>
<p> Consider a cell structure in 2 dimensions.</p>
<ol><li>Using <a href="http://en.wikipedia.org/wiki/Euler_characteristic" title="Euler's polyhedron formula">Euler's polyhedron formula</a>, which states that for a convex polyhedron, V-E+F = 2, where V, E, and F are the vertices, edges and faces of the polyhedron, </li>
<li>assuming isotropic energy (and equal mobility) for all the cell walls, and </li>
<li>assuming that triple junctions are points at which the cell walls make 120 degrees with each other (in other words, achieve equilibrium),</li>
</ol><p> <a href="http://en.wikipedia.org/wiki/John_von_Neumann" title="Neumann wiki">von Neumann</a> showed that six sided cells are stable; the grains with sides greater than six sides grow while those with less than six sides shrink. Neumann made the assumption that the curvature of each of the walls is a constant. <a href="http://www.materials.cmu.edu/rohrer/mullins/wwmullins.html" title="Mullins homepage">Mullins</a> relaxed the curvature condition, and showed that the result holds even if the curvature is not a constant--mean curvature is what matters. Thus, Neumann's results are valid for soap froths, while that of Mullins is valid even for grain boundaries--albeit in two dimensions. This is a purely topological result and can also be derived using <a href="http://en.wikipedia.org/wiki/Gauss%E2%80%93Bonnet_theorem" title="Gauss-Bonnet theorem">Gauss-Bonnet theorem</a> -- see the derivation given by <a href="http://www.imm.rwth-aachen.de/hp/person/gg/gg_en.htm" title="Gottstein webpage">Guenter Gottstein</a> and Lasar S Svindlerman in <a href="http://www.amazon.com/Grain-Boundary-Migration-Metals-Thermodynamics/dp/084938222X" title="Grain boundary migration book">Grain boundary migration in metals: Thermodynamics, Kinetics</a>, pp. 309-310, CRC Press, New York 1999, for example.</p>
<p> <span>3D (and N) generalization to von Neumann-Mullins relation<br /></span><br /> Apparently, there had been several attempts to generalize the Neumann-Mullins to 3D in vain, so far. MacPherson and Srolovitz manage to do just that--in the process, they also obtain an N-dimensional<span> </span>generalization. The idea behind the derivation of such a generalized result is as follows:</p>
<ol><li>Generalize Neumann-Mullins to multiply connected domains in 2D; and,</li>
<li>Volume integrate the result.</li>
</ol><p> Obviously, the two step process is nothing but considering all possible 2D sections of the given 3D structure, doing a 2D Neumann-Mullins analysis on each of them, and putting the results of all these analyses together. And, this is also the point where things become a bit (too) mathematical. </p>
<p> In any case, I understand that the net result of the two step process described above is the introduction of a natural measure of length--called mean width--and this measure is a <a href="http://en.wikipedia.org/wiki/Hadwiger%27s_theorem" title="Hadwiger measure">Hadwiger measure</a>. And, the Neumann-Mullins result can be stated in terms of the Hadwiger measures in N dimensions, of which, the 2D and 3D results become a special case. And, the result also shows that in 3- and higher dimensions, the result is not purely topological.</p>
<p> <span>What next?</span></p>
<p> In real systems, say, a grain boundary, for example, the boundary energies are anisotropic; the mobilities are not constant; the triple junctions induce drag on the boundary motion -- Or, in other words, each of the assumptions made by Neumann, Mullins, MacPherson, and Srolovitz are to be relaxed. Thus, this is but a first step in the search for an understanding of grain growth and coarsening studies.</p>
<p> <span>Relevant links</span></p>
<p> <a href="http://mogadalai.wordpress.com/2006/10/30/grain-growth-beyond-von-neumann-mullins/" title="Beyond Neuymann-Mullins blogpost">Most of this post is based on this blog post of mine</a>. I have also <a href="http://http//mogadalai.wordpress.com/2007/04/26/grain-growth-beyond-von-neumann-mullins-edition-2/" title="Beyond Neumann-Mullins --2nd edition">collected the links</a> to the <a href="http://dx.doi.org/10.1038/nature05745" title="Paper of MacPherson and Srolovitz">paper of MacPherson and Srolovitz</a>, the <a href="http://www.nature.com/nature/journal/v446/n7139/suppinfo/nature05745.html" title="Supplementary information to MacPherson and Srolovitz paper">supplementary information to the paper</a>, the <a href="http://dx.doi.org/10.1038/446995a" title="News and Views piece on the Nature paper">News and Views piece on the work by David Kinderlehrer</a>, and the <a href="http://www.sciam.com/article.cfm?chanID=sa003&articleID=29A52001-E7F2-99DF-34AF7AB8412D860A&ref=rss" title="SciAm on the beer froth paper">Scientific American news report</a>.</p>
<p> Have fun!</p>
</div></div></div>Fri, 27 Apr 2007 08:12:20 +0000Mogadalai Gururajan1302 at https://imechanica.orghttps://imechanica.org/node/1302#commentshttps://imechanica.org/crss/node/1302