Material Science Seminar

The Relationship Between Crystallographic Pitting and Metallic Bonding. Dr. Scott LillardMaterials Science & Technology Division
Los Alamos National Laboratory
Los Alamos, New Mexico Over the past half-century numerous authors have reported relationships between pitting corrosion and crystallographic orientation (for example vs. directions). This phenomenon is commonly referred to as corrosion etch pitting and the observations associated with it can generally be divided into two categories: 1) relationships between pitting susceptibility (initiation) and crystallographic orientation and 2) relationships between pit morphology (propagation) and crystallographic orientation. The formation of corrosion etch pits in metals, both initiation and propagation, is often attributed to surface energy. Surface energy is a fairly general term used to describe dangling bonds at a free surface - more closely packed surfaces having lower surface energy as they loose the fewest number of bonds per unit area when the new surface is formed. However, this simple "hard-sphere" model of the surface does not predict experimental observations in etch pitting. This does not mean that bonding does not play a role in etch pitting, rather, that our method or calculating surface properties needs to be improved. Here, we introduce a novel materials simulation method to quantify the influence of coordination-dependent bonding on etch pitting. In our model surface properties arising from metal-metal bonding are evaluated by calculating atomic embedding energies. We will introduce this method and demonstrate its accuracy by comparing predicted pit morphologies in magnesium with those calculated in our model.Scott Lillard is a Technical Staff Member in the Materials Science & Technology Division of the Los Alamos National Laboratory. He received his Ph.D. in Materials Science and Engineering from the G.W. Whiting School of Engineering at the Johns Hopkins University in 1992. He is the author of over 50 technical publications in the field of corrosion and is on the editorial boards of Corrosion, Journal of Materials Research, and Journal of Corrosion Science Engineering and Technology. His interests include experimental research in the areas of localized corrosion, oxide films, environmental fracture, and hydrogen reaction kinetics.All first year MASC students are required to attend.Refreshments will be provided.

Location: John Stauffer Science Lecture Hall (SLH) - 102

Audiences: Everyone Is Invited

Contact: Petra Pearce