How Grain Growth Stops: A Mechanism for Grain-Growth Stagnation in Pure Materials

• Published in: Science (American Association for the Advancement of Science) Vol. 328; no. 5982; pp. 1138 - 1141
• Main Authors: Holm, Elizabeth A., Foiles, Stephen M.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 28.05.2010; The American Association for the Advancement of Science
• Subjects: Boundaries; Condensed matter: structure, mechanical and thermal properties; Crystal structure; Crystallization; Defects and impurities in crystals; microstructure; Exact sciences and technology; Grain and twin boundaries; Grain boundaries; Grain growth; Grain size; High temperature; Kinetics; Low temperature; Materials; Materials science; Nanocrystals; Physics; Plugs; Polycrystals; Roughening; Solutes; Stagnation; Structure of solids and liquids; crystallography; Thermodynamic equilibrium; Thermodynamics; Grain boundaries; Annealing; Mesoscale; Grain growth; Growth mechanism; Molecular dynamics method; Polycrystals; Grain boundary migration; Thermodynamic equilibrium
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1187833

The thermodynamic equilibrium state of crystalline materials is a single crystal; however, polycrystalline grain growth almost always stops before this state is reached. Although typically attributed to solute drag, grain-growth stagnation occurs, even in high-purity materials. Recent studies indicate that grain boundaries undergo thermal roughening associated with an abrupt mobility change, so that at typical annealing temperatures, polycrystals will contain both smooth (slow) and rough (fast) boundaries. Mesoscale grain-growth models, validated by large-scale polycrystalline molecular dynamics simulations, show that even small fractions of smooth, slow boundaries can stop grain growth. We conclude that grain-boundary roughening provides an alternate stagnation mechanism that applies even to high-purity materials.