Doug Spearot, Ph.D.
Assistant Professor of Mechanical Engineering
University of Arkansas, Fayetteville
Computational Materials Science Research
The global objective of Spearot’s research is to explore material behavior on the nanoscale for the purposes of developing multiscale structure-property relationships in mechanics of materials. Nanoscale material behavior is studied using atomistic simulation techniques, including Monte Carlo, molecular mechanics and molecular dynamics simulations. Of particular interest is the impact of defects (interfaces, dislocations, surfaces, etc.) on material properties. For example, one of Spearot’s current research projects focuses on grain growth and plastic deformation in solute-modified nanocrystalline Cu. Solute-modification is necessary in metallic nanocrystalline materials to prevent abnormal grain growth at low homologous temperatures, which is a critical road-block preventing the use of metallic nanocrystalline materials in high temperature applications. Spearot, along with his collaborators show via molecular dynamics simulations that grain growth can be suppressed with very low concentrations of specific dopant elements positioned at the grain boundaries and triple junctions. More importantly, Spearot’s research shows that grain boundary sources for dislocations in nanocrystalline samples are not appreciably impacted by the presence of the carefully chosen dopant; grain boundary ledges and triple junction regions still dominate as dislocation sources in metallic nanocrystalline materials. Thus, grain stabilization is achieved in these samples without negatively impacting the native properties of the nanocrystalline material, such as strength or ductility. Spearot’s work is unique in that grain stabilization is achieved by using very small amounts of carefully selected solute atoms (< 1 at.%), as many previous experimental efforts use significantly higher dopant concentrations (> 10 at.%) to suppress grain growth, which has a deleterious effect on nanocrystalline material properties. Other research interests of Spearot include modeling dislocations in confined volumes, such as those characteristic of nanolaminate samples, and linking mesoscale models of material behavior to atomistic simulations. As a result of his research efforts and future promise, Spearot received the 2007 Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associated Universities in Engineering and Applied Science.
MD simulation model of nanocrystalline Cu- 0.5 at.%Sb containing 135 grains with average grain diameter of 15 nm. The different colors represent individual grains and the Sb atoms are colored red and placed at the grain boundaries. Simulation contains approximately 20 million atoms.
Plastic deformation of the nanocrystalline Cu-0.5 at.%Sb alloy with average grain diameter of 15 nm at (a) 0.0% strain (b) 4.5% strain (c) 7.5% strain. Atoms are colored by the centrosymmetry parameter and dislocations are identified by linear stacking fault debris within each grain connecting back to the grain boundaries.