MSE Colloquium: Martin Harmer, "Grain Boundary Complexions – My Entrée Into Metallurgy"

Center for Advanced Materials and Nanotechnology, Dept. of Materials Science and Engineering, Lehigh University, Bethlehem, PA

Abstract

Grain boundaries exhibit phase-like behavior in which their structure, chemistry, and properties may change discontinuously at critical values of thermodynamic parameters such as temperature, pressure, and chemical potential. Therefore, grain boundaries (and other interfaces such as surfaces and heterophase boundaries) can be treated as thermodynamically stable interfacial states. To differentiate these interfacial states from bulk phases, the term ‘complexion’ has been introduced. The field of grain boundary complexions has evolved rapidly in the past decade due to advances in experimental equipment – in particular, aberration-corrected transmission electron microscopy – and progress in computational simulation methods. Grain boundary complexion transitions are the root cause of a wide variety of materials phenomena – such as abnormal grain growth and activated sintering – that have defied mechanistic explanation for years. In this colloquium, I will review the history and theory of grain boundary complexion transitions, their role in materials processing, and their effect on materials properties.

Bio

Professor Harmer is the Alcoa Foundation Professor of Materials Science and Engineering and Director of the Center for Advanced Materials and Nanotechnology at Lehigh University.  He obtained his B.Sc., Ph.D., and D.Sc., Degree in Ceramics from Leeds University in England.  He spent the majority of his career working on ceramic materials, but more recently has branched out into the field of metallurgy.  He has received numerous awards from the American Ceramic Society including the W. David Kingery Award, the Sosman Memorial Lecturer Award, the Fulrath Award, and the Ross Coffin Purdy Award.  He is an ISI highly cited researcher and a Fellow of the American Ceramic Society.  He has received the Kuczynski prize for sintering and the Humboldt prize for senior scientists.  He is an Editor for Acta Materialia.  In his spare time he enjoys captaining the Cheeky Monkey II Sport fisher as a U.S. Coast Guard Licensed Merchant Marine Officer.