How do defects and minor solute control the corrosion properties of solid solution alloys?

1. CORROSION MECHANISMS IN AMORPHOUS SOLID SOLUTION ALLOYS: Role(s) of Minor Alloying ElementsJohn R. Scully, University of Virginia Main Campus, DMR 0906663 • How do defects and minor solute control the corrosion properties of solid solution alloys? • Investigation of the effects of structural (order – disorder transformation, relaxation), chemical (solute clusters, minor solute elements) and structural/chemical defects (solute rich and lean nanocrystals in an amorphous solid solution) were conducted at the nm-scale on corrosion using model engineered materials. • Disordered and ordered crystalline Fe50Pd50 show similar behavior in acidic Cl- solution, but the disordered structure has strong grain orientation dependent dissolution which is morphologically different than after ordering [1] • The addition of minor solute elements alters the corrosion resistance of amorphous Al-Cu-Mg based alloys. Ni alloying lowers dissolution rate of Al. Ni also suppresses surface diffusion enabling the formation of a finer porous structure upon dealloying. Dealloying also leads to a rearrangement of Cu to the energetically favorable crystalline phase [2] Disordered Fe50Pd50 Ordered Fe50Pd50 [1] Key result: Structure and compositional ordering play a role in corrosion behavior Disordered Fe50Pd50 (101) EBSD Grain Orientation Index (100) [2] Amorphous Alloy Amorphous alloy with Ni With Ni No Ni Mg With Ni No Ni Cu Mg Al Al Al Mg Al Cu Al Al Al Cu Al Cu Mg Mg Al Mg Al Al Pure Al Al Cu Cu Mg Al Al Cu Al Al Al Al Mg Cu Al Amorphous Alloy with beneficial minor solute Amorphous alloy no Ni Crystallization by dealloying Ni Nanoporous Cu formed in pits Cu Al Electrochemistry Cu Cu Al Al Al Mg Al Al Ni Al Mg Cu Al Key results: Minor alloying element (Ni) plays an important role in the local corrosion behavior as well as dealloying of solid solutions. The solute rich amorphous alloys reorganizes into crystalline structure as dealloying proceeds. Al Al Al Al Al Cu Cu Al Cu Mg Al Al Al Al Ni Cu Al Mg Cu Mg Al Cu

2. CORROSION MECHANISMS IN AMORPHOUS ALLOYS: CRITICAL COMPOSITIONAL AND STRUCTURAL DEFECTS FOR LOCAL CORROSION John R. Scully, University of Virginia Main Campus, DMR 0906663 Spatio-temporal Chaos in Systems of Broken SymmetryEberhardBodenschatz, Cornell University, DMR Award#0072077 (Title) IIName, Institution, DMR Award# • Corrosion Education • One high school (Martha Fox), 2 Undergraduates (H. Bindig, W. McCarthy), 3 graduate students (T. Aburada, N. Tailleart, D. Horton), and 1 post-doctoral researchers (H. Ha) contributed to NSF-supported project. • Graduate & undergraduate, courses in corrosion taught in class and via distance learning (MSE 7080) and MSE 3080 for Made-in-Virginia for Engineers that brings engineering education to workers • John R. Scully served on National Academy Study on Research Opportunities In Corrosion (ROCSE). Report due Fall 2010. Co-authors for Inaugural Best Paper in Corrosion Journal Award Recipients for NSF Funded Work on Amorphous Al-Co-Ce • Outreach • NanoDays participation with nano-scale corrosion applications at local schools and museums • cKITs (a set of corrosion experiments)supplied by National Association of Corrosion Engineers supplied to local K-12 schools • Materials science and engineering demonstrations and lab tours are given to foster an interest in the physical sciences and materials science. Awards and Honors • Nicole Tailleart, John R. Scully: Inaugural Award Recipients of the Corrosion Journal Best Paper Award, "User-selectable Barrier, Sacrificial Anode, and Active Corrosion Inhibiting Properties of Al-Co-Ce Alloys for Coating Applications." NACE International Conference, San Antonio, TX 2010. • UVA's Center for Electrochemical Science and Engineering received the 2009 NACE Distinguished Organization Award • John R. Scully: received the H.H. Uhlig Award, 2009 of the Electrochemical Society for excellence in corrosion research. • Tomohiro Aburada was: One of twelve invited students internationally to present at Gordon Research Seminar, New London, NH 2010.