| Abstract: | A chronological summary is given of the various types of grain boundary fracture found in metals. In each case, there is an
impurity that adsorbs at the new (fracture) surface being formed. For the case of Fe-P alloys, a quantitative argument can
show that adsorption of phosphorous on the free surface greatly reduces the barrier to void nucleation compared to that in
the absence of phosphorous. The same or larger reduction would appear for any other element, which adsorbs more strongly than
phosphorous and displaces it at the surface. Such an argument is shown to explain a great many cases of dimpled grain boundary
fracture in strong alloys undergoing creep or hydrogen attack. The reduction in surface energy can also lead to a smooth grain
boundary fracture (no void nucleation), in which diffusion of solute to the new surface limits crack growth. Numerous examples
of this are also discussed.
Dr. Shewmon studied metallurgical engineering at the University of Illinois (B.S. 1952) and Carnegie Institute of Technology
(Ph.D. 1955). His first job was at the Westinghouse Research Laboratory, where he studied thermal diffusion in alloys and
surface diffusion. In 1958, he moved to the Carnegie Institute of Technology, where he served as a professor until 1967. The
text “Diffusion in Solids” was published in 1963. An NSF Fellowship was used to study at Professor C. Wagner’s Max Planck
Institute (Goettingen, Germany) in 1963.
From 1968 to 1973, he was at Argonne National Laboratory, serving successively as Associate Director of the Metallurgy Division,
Associate Director of the EBR-2 Project, and Director of the Materials Science Division. The text “Transformations in Metals”
was published in 1969. Materials behavior in fast breeder reactors was the main theme of his work during this period.
He was the director of the Division of Materials Research at the National Science Foundation from 1973 to 1975. From 1975
to 1993, he was Professor at Ohio State University in the Department of Metallurgical Engineering (later Materials Science
and Engineering), serving as Chairman from 1975 to 1983. Research interests during this period were hard particle erosion
and hydrogen-induced cracking of steel (“hydrogen attack”). From 1977 to 1993 he served on the Advisory Committee on Reactor
Safety for the United States Nuclear Regulations Committee, serving as Chair for three of those years.
Dr. Shewmon was elected to the National Academy of Engineering in 1979 and has been awarded the standing of Fellow in TMS,
ASM, ANS, and AAAS. He has received several outstanding paper awards (Noble-AIME, Raymond—TMS, Mathewson—TMS, and Howe—ASM).
He received the Distinguished Alumnus Award of the University of Illinois in 1981 and a Humboldt Foundation Senior Scientist
Prize in 1984.
The Edward DeMille Campbell Memorial Lecture was established in 1926 as an annual lecture in memory of and in recognition
of the outstanding scientific contributions to the metallurgical profession by a distinguished educator who was blind for
all but two years of his professional life. It recognizes demonstrated ability in metallurgical science and engineering.
The Institute of Metals Lecture was established in 1921, at which time the Institute of Metals Division was the only professional
division within the American Institute of Mining and Metallurgical Engineers. It has been given annually since 1922 by distinguished
people from this country and abroad. Beginning in 1973 and thereafter, the person selected to deliver the lecture will be
known as the “Institute of Metals Division Lecturer and R.F. Mehl Medalist” for that year. |
