BULLETIN: Is there one particular item on your agenda for MRS in 1989 that you believe needs to receive highest priority?

CHANG: Having spent the time putting together a preliminary 5-10 year plan for MRS, I find that we have several areas of priority for 1989: 1. The Headquarters needs a new computer/software system immediately in order to keep the Society moving smoothly. 2. The ratio of the Society reserve to cash flow has fallen precipitously over the last couple of years due to our rapid growth. This needs to be taken care of starting this year. 3. MRS needs to work with other materials societies to better serve the materials community at large. 4. MRS needs more activities at the Section and Chapter levels. 5. Increased visibility is needed for Journal of Materials Research in 1989.

BULLETIN: We've heard many explanations for the particularly rapid expansion of MRS membership and activities. Can you give us your perspective on what the underlying driving force behind this growth is?

CHANG: MRS is a member-driven society, and because of this many opportunities are made possible. We provide the best opportunity for members to organize new and novel materials symposia. Our meetings are structured to enhance cross fertilization among the various materials disciplines. We emphasize quality in whatever we do with our limited resources. We have a first-rate publications department that provides rapid dissemination of technical information. In short, our members are involved in every aspect of MRS operations, and their good ideas are always implemented.

This article provides an overview of the piezoelectric effect in all the classes of materials in which it is found to occur. This includes select materials from the categories of naturally occurring single crystals, polycrystalline ceramics, and semicrystalline polymers. Throughout this development, an attempt is made to point out the common factor for the piezoelectric effect in all these materials, namely, the presence of dipolar moieties, whose orientation brings about a net polarization in the material as a whole.

The applications of each of these classes of materials are covered briefly. Each such application has a specific value based on the aggregate properties of the material as a whole, making each material complementary rather than competitive in device applications.

Brief mention is made of the mathematics and geometry of the piezoelectric effect in order to define the piezoelectric constants by which the properties of these materials are described. The article then focuses on the basis of the piezoelectric response in synthetic polymers.

Piezoelectricity or “pressure electricity” was coined from the Greek verb “piezen,” to press, by Pierre and Jacques Curie in the 1880s during an investigation of the symmetry in crystals. In this work it was found that certain crystals, lacking a center of symmetry, produced an electrical charge when mechanically deformed. The converse effect was also found to occur, whereby applying an electric field caused the crystal to change its shape. This phenomenon was attributed to a deformation of the net internal polarization in the crystal. When no external forces are present, the centers of positive and negative charges will coincide, and there is no net polarization. The application of a stress, be it mechanical (pressure) or electrical (applied field), causes a displacement of the centers of gravity of the positive and negative charges. In the absence of a center of symmetry, the charge displacement will be nonsymmetrical and thereby produce an induced dipole moment. This dipole moment, if produced by a mechanical stress, will cause the surfaces to develop an effective charge. If an external field displaces the charges, by electrostatic attraction or repulsion, it produces a mechanical strain which causes the material to deform. The mathematical relations describing this effect were developed in the few years following their discovery, making use of tensor notation to describe the directionality of the applied stress and the resultant strain.

Welding science is an interdisciplinary field involving metallurgy and materials science, heat, fluid, and mass transfer, and arc and plasma physics to name a few. Three areas of welding science have been the focus of much research the past few years as welding scientists attempt to understand the phenomena responsible for producing fusion welds with acceptable service properties. Broadly defined, these areas are:

1. physical and numerical modeling of the heat and fluid flow during fusion welding,

2. understanding the microstructural evolution during solidification and cooling of welds, and

3. welding of advanced materials.

This short review will focus on these fusion welding research themes to provide the reader with a flavor of the work in progress at several major government, industry, and university laboratories.

Much of both the experimental and theoretical studies that have advanced the understanding of fusion welding processes revolves around delineating the roles of mass, momentum, and energy transfer. The earliest models of fusion welding processes were analytical models of heat transfer by conduction. These models not only excluded much of the physics of the process, but assumed point or linear heat sources. Nevertheless, these models provided useful insight about the interplay between power and weld speed, particularly regarding weld pool shape. Also, although quantitative predictions of weld pool shape were generally inaccurate, predicted thermal contours and cooling rates away from the fusion zone were useful in understanding the extent of heat-affected zones.

Chaired by G. Slade Cargill, III (IBM Watson Research Center), D. Wayne Goodman (Texas A & M University), and J. Francis Young (University of Illinois), the 1988 MRS Fall Meeting was the largest on record. A strong and varied program of 24 technical symposia attracted over 3,700 participants from Monday, November 28 to Friday, December 4. Rounding out the meeting program were the lunchtime tutorial lectures of Symposium X, Frontiers of Materials Research; a forum on the Materials Science and Engineering Study, which previewed the forthcoming National Research Council report; the Plenary Address by Prof. Lester C. Thurow (Dean of the Sloan School of Management, Massachusetts Institute of Technology) on “Maintaining Technological Leadership in a World Economy”; and the presentation of the 1988 Von Hippel Award to Prof. Jacques Friedet (Professor of Solid State Physics, University of Paris).

The lectures by Thurow and Friedel were both excellent presentations, although quite different in style. Thurow confounded the scientists' cynical view of economists by giving a lucid and cogently argued presentation of the societal problems underlying the loss of United States dominance in technological developments. Readers will be able to peruse the text in an upcoming issue of the MRS BULLETIN but will miss the flavor of the oral presentation. Prof. Friedel gave a delightful personal account of his scientific career, which illustrated so well the unity of materials research despite the apparent diversity of approach. His account is published elsewhere in this issue.

It is an honor to receive the Arthur von Hippel Award, and to become a member of such a select club! It is also a great pleasure to be introduced by my friend Harvey Brooks, who, with his wife Helen, were the first Americans to greet me on my first trip here in 1953.

What has an aging theoretical physicist to do with such a young and budding society as yours? I can only comment on this difficult question by reflecting on the way some of my work has proceeded, and what light this might throw on the development of materials research. I will concentrate on two topics which have been at the core of my work.

I stated research in 1948, under my cousin Charles Crussard, at the Laboratory of Metallurgy of the Paris School of Mines, after a thorough training in mathematics, some training in classical physics and chemistry, and two years of more technical training in mining and metallurgy. I started pulling at test samples and tried to get interested in internal friction. I also learned about x-rays on an old tube set up by my father Edmond Friedel in 1920 at Maurice de Broglie's laboratory, to check the prediction of a layer structure for “smectic” mesophases made by his own father Georges Friedel. I finally used this tube in a very simple piece of experimental work where I measured the angles made at triple nodes by grain boundaries in a sheet of recrystallized aluminum. The idea was to deduce how the grain boundary tension varies with the relative misorientation of the two grains, having checked that the tension does not vary much with the orientation of the boundary with respect to the crystals, a remark that justifies the method.