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BRUCE CHALMERS October I5, I907-May 25, 1990 BY DAVID TURNBULL BRUCE CHALMERS HAD A notable career as a scientist, edu- cator, en c! editor. He outTinec! his career in his profes- sional biography, which was published in the thirtieth anni- versary volume) of "Progress in Materials Science," a series for which he was the founcler-eclitor. This volume, consist- ing of articles by some of his former students en c! profes- sional colleagues, was publisher! to honor him. I have re- liec! heavily on that accounts in preparing this memoir. Bruce was born in ~ 907, a son of Stephen en c! Clara (Rosenhain) Chalmers, en c! was rearm! in Lonclon. His fa- ther, a clescenclent of the Scottish Camerons, was a math- ematics teacher, he cliec! in 1919, when Bruce was twelve years oIcI. Bruce's inclination towarc! science clevelopec! quite early en c! was stimulates! in part by his father en c! especially his oIcler brother Alan, who became a physicist en c! profes- sor at the University of Durham. However, the major influ- ence on his choice of career was that of his maternal uncle, Walter Rosenhain, a leacling metallurgist who, cluring WorIc! War I, was superintendent of the Department of Metallurgy en c! Metallurgical Chemistry in the National Physical Labo- ratory. Rosenhain became well known for cleveloping one of the earliest moclels for intercrystalline boundary struc 77

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78 BIOGRAPHICAL MEMOIRS sure. It is interesting that Bruce came, by a somewhat cir- cuitous route, to play a leacling role in cleveloping the much more sophisticates! moclern theory for such structures. In a review publisher! in 1917,3 Rosenhain wrote with great clarity en c! eloquence of the emergence of a "New Metallurgy" baser! on funciamental research in chemistry en c! physics. Bruce's career contributes! greatly to the cle- velopment of strong boncis between metallurgy en c! physics en c! chemistry, en c! the continues! advancement of the "New Metallurgy", but with somewhat more emphasis on the met- allurgy bone! to physics than to chemistry. Bruce lived at home throughout his secondary and uni- versity training. He attenclec! University College of London University en c! earnec! a B.Sc. in physics in two years, by- passing the normally requires! thirc! year. He was acceptec! as a Ph.D. student by Professor of Physics E. N. DaC. Andrade. Bruce was highly inspirer! by Anciracle, both for his achieve- ments as a scientist en c! as an educator. Anciracle in 1910 "was one of the first to recognize that the mechanical be- havior of metals conic! properly be regarclec! as a problem in physics." He cliscoverec! the tiff law of creep. For his Ph.D. thesis, Anciracle suggester! that Bruce investigate the change in resistivity accompanying the creep of metals with a hexagonal crystal structure, such as cadmium. IncleecI, the resistivity did change with deformation, reflecting the change in crystallographic orientation with slip. In connec- tion with his investigation, Bruce hac! to put together X-ray diffraction equipment, which was then lacking in the phys- ics department. Bruce learner! much from Anciracle about how a professor en c! research student shouIc! interact most effectively. Bruce greatly acimirec! Anciracle's way with re- search students, which was to have them work with him rather than for him and to allocate credit fairly for any discoveries. Bruce received his Ph.D. degree in 1932 during the depth

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BRUCE CHALMERS 79 of the Great Depression, when positions were clifficult to find. After a year of postdoctoral study he was appointed lecturer in physics at Sir John Cass College of London Uni- versity, a technical institute that mainly servec! part-time evening students who hac! taken inclustrial jobs immecli- ately following their secondary education. Bruce taught in the evenings five times weekly, so his clays were more or less free for research. At this time, many physicists sharer! Anciracle's interest in the plastic properties of single crystals, and G. I. Taylor, Egon Orowan, en c! others were cleveloping the clisIocation moclels for plastic flow. Bruce was cir awn into these activi- ties, en c! he clevisec! high precision measurements of plastic creep rates of single crystals at low stress levels. He clevel- opec! a simple methoc! of growing tin single crystals with any specified crystallographic orientation. Understanding the flow behavior of single crystals wouIc! be essential to interpreting that of the more complicates! polycrystalline solicis. In the course of his investigations, Bruce fount! that one of his presumer! single crystals actually was composer! of two crystals separates! by a boundary along the entire length of the cylincirical specimen. From visual en c! optical microscope observations, he notes! that all the crystals he grew exhibiter! sub-bounciaries en c! other imperfections. The origin, structure, en c! property effects of these imperfec- tions fascinates! Bruce, en c! they became the focus of his research throughout his career. After five years at Cass, Bruce acceptec! a position as physi- cist at the Tin Research Institute, a laboratory sponsorec! by the International Tin Research en c! Development Council. In aciclition to his studies of the mechanical behavior of tin, he investigated the physics of the process of making tin plate by clipping steel into molten tin. He was requires! to clevelop methods for examining the micro-topography of

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80 BIOGRAPHICAL MEMOIRS the surface of the tin layer en c! to clo theoretical work on the origin of the porosity often present in the layer. In 1938 Bruce marries! Ema Arnouts, who was a warm en c! supportive companion throughout his life. They be- came the parents of one son, Stephen, en c! four daughters, Carol, lane, Alison, en c! Heather. Soon after the beginning of Woric! War II, Bruce joiner! the metals research section of the British Ministry of Sup- ply, en c! he investigatec! the heat treatment of armor pierc- ing shot en c! the non-clestructive evaluation of their quality. Early in 1944 he was appointed head of the Metallurgy Divi- sion of the Royal Aircraft Establishment at Farnborough, where he was concernec! with problems of materials fail- ures, as in aircraft crashes, en c! clevelopment of alloys with high strength en c! low density. These problems lee! him more cleeply into the general area of structure-property relations, which are central to physical metallurgy. In 1946 he joiner! the Atomic Energy Research Establish- ment opening at Harwell as heat! of its Metallurgy Division. There he formulates! a program clirectec! at the clevelop- ment of nuclear reactor materials en c! assemblec! a research staff to carry it out. His staff members remember him as an inspiring leacler, but he fount! the burclens en c! bureau- cratic controversies attending administration quite distaste- ful. Having enjoyed his teaching experience at Cass, he was attractor! to the possibility of returning to academia. This prospect soon materializecI, en c! in 1948 he became a professor of physical metallurgy at the University of Toronto. At Toronto he attractor! a large group of students in whom he arouser! a great enthusiasm for metallurgical research. It was his practice to have most of his research group accom- pany him to National Metallurgical Society meetings in the Uniter! States, where Bruce introclucec! them to leacling sci- entists. The students eagerly attenclec! the technical sessions

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BRUCE CHALMERS 81 en c! at intercessions boicITy assailer! the speakers with icleas en c! often-embarrassing questions about their results. This practice of promoting student participation in sci- entific meetings reflects his sagacity as an educator en c! the close, corclial relations he always hac! with his students at Toronto en c! later at Harvard. He en c! his students per- formec! the experiments en c! analyses that lair! the founcia- tions of our present unclerstancling of the origin en c! na- ture of the grain and subgrain morphology formed in the crystallization of liquicis. Their analyses took clue account of the heat en c! material transport en c! interface movement en c! morphology attending crystallization. Especially impor- tant was their concept of "constitutional unclercooling", which accountec! for the role of impurities in the clevelopment of cellular en c! clenciritic structures. He en c! student Karl Aust at Toronto grew sets of tin en c! leac! bicrystals with a range of misorientations en c! measurer! the relative grain bouncI- ary energy clepenclences on the crystallographic misorien- tations. These energies en c! those of FeSi alloys measurer! inclepenclently by C. B. Dunn at General Electric were in remarkable agreement with the predictions of the clisIoca tion mocle! for tiTt-type grain boundaries clevelopec! at Bell Labs by W. T. React en c! William Shockley. In 1953 Bruce acceptec! appointment as Gordon McKay professor of metallurgy in the Division of Applier! Sciences at Harvarc! University. This position attractor! him in part because the absence of clepartmental boundaries wouIc! per- mit him to interact freely with the solic! state physics en c! applier! mechanics groups in the division. Then, en c! for a consiclerable time thereafter, graduate students were acimit- tec! to the division en c! to the physics department with no initial commitment to any professor. Thus, they hac! one to two years to explore possible Ph.D. thesis topics en c! to seek an Divisor. This policy meant that each professor hac! ac

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82 BIOGRAPHICAL MEMOIRS cess to a brilliant group of students, en c! Bruce en c! his successors in the materials science-metallurgy option ben- efited greatly from it. During the perioc! 1930-70 in the Uniter! States en c! Eu- rope there was extensive interdisciplinary cooperation of metallurgists with physicists, physical chemists, en c! applier! mechanicians, which transformer! metallurgy from an art to a science en c! lair! the foundation for what we now label materials science. Among the physicists en c! physical chem- ists who were most prominent in effecting this transforma- tion were Frederick Seitz, Clarence Zener, Conyers Her- ring, Charles Frank, Nevill Mott, W. Shockley, John Barcleen, en c! Harvey Brooks. From the metallurgical sicle there were Cyril Stanley Smith, L. S. Darken, Alan Cottrell, Morris Cohen, Paul Beck, R. F. Mehl, C. S. Barrett, A. Guinier, I. H. Hollomon, en c! other members of his group at the General Electric Research Laboratory. Through his activities as a scientist en c! editor, Bruce playact a central role in this transformation. He was the founcling editor of the continuing series of treatises "Progress in Metal Physics," now "Progress in Materials Science." Bruce en c! co-eclitors RonaTc! King. W. Hume-Rothery, l. W. Christian, en c! T. B. Massalski, who joiner! him from time to time, attracted! a very clistinguishec! group of contributors from diverse fields. These volumes were highly influential all over the worIc! in the education of graduate students studying metallurgy, solid mechanics, and materials science gener- ally. They also playact an important part in clefining the scope en c! limits of materials science. Later Bruce became the first and longtime editor of a newly founded (in 1953) journal Acta Metallurg~ca (now Acta Materiatia). This journal was founclec! in response to the impression that the metal- lurgical society journals hac! become too limiter! in their scope and too permissive on the quality of the papers they . .

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BRUCE CHALMERS 83 accepted. Bruce imposer! high stanciarcis for publication, as he clic! for articles solicitor! for the Progress series. Acta Metatturg~ca became the journal of choice for metallurgists en c! other materials scientists woric~w~cle, en c! with the Progress volumes it set the stanciarc! for research in these areas. While imposing high stanciarcis on the papers accepted, Bruce was highly receptive to new icleas en c! theories en c! exer- cisec! a liberal policy on their acceptability for publication. Capt. Robert Maxwell's Pergamon Press publisher! Acta Metallurg~ca en c! ultimately the Progress volumes. Bruce hac! a sometimes-aciversarial relation with Maxwell, who from Bruce's standpoint was often too concernec! with the com- mercial aspects of publishing scientific articles. At Harvard, Bruce continues! to guicle research on solicli- fication en c! the structure en c! behavior of grain bouncI- aries. He en c! his students clemonstratec! that the appear- ance of equiaxec! grain structures in the crystallization of pure liquicis generally results from clenciritic breakup. Of- ten this breakup is effecter! by convective currents in the liquicI. They shower! that, when these currents are suppressed in molten aluminum by imposition of a magnetic fielcI, a columnar morphology forms in crystallization uncler concli- tions where an equiaxec! one normally would have appeared. Also, they clevelopec! a beautiful visual demonstration of clenciritic breakup in the freezing of water in an "ice ma- chine" programmer! to cycle water between a temperature above its freezing point en c! a lower temperature at the point of clenciritic breakup. This experiment was on exhibit at the Brussels WorIcl's Fair in 195S, en c! is now sometimes clisplayoc! at the Boston Museum of Science. At Harvard, he also wrote several books, one of which was the wiclely cites! Principles of Solidification (1964), two other books were Physical Metallurgy en c! Energy. Most of his students en c! postcloctorals were stimulatecI, partly by his

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84 BIOGRAPHICAL MEMOIRS example, to cleclicate their entire careers to science, en c! many have achiever! distinction in academia, government, en c! inclustrial high-technology laboratories. He en c! I were colleagues at Harvarc! from 1962 on. When we cliscussec! theoretical icleas or moclels, he always focuses! on the ex- perimental support for them. In his quiet low-key way, he exertec! tremendous influence on the clevelopment of in- terclisciplinary relations en c! the consciousness of a materi- als science boncling the unclerlying clisciplines. In the latter part of his Harvarc! career, Bruce clevelopec! a strong interest in unclergracluate education, en c! in 1964 President Pusey appointee! him master of Winthrop House. Pusey noted Bruce's remarkably broad intellectual perspec- tive en c! his creep appreciation of the humanities. From my association with Bruce, I can attest to his wicle knowlecige of literature en c! to his creep insights into history en c! poli- tics. The Harvarc! houses were patternec! after the college system of Cambridge and Oxford. While each provided a community for about 400 students, they never acquirer! the central eclucational en c! policy roles in the university that the British colleges have. Nevertheless, Bruce with Ema's enthusiastic support fostered a friendly, intellectually vibrant atmosphere in Winthrop House. Often outstanding persons in a variety of fields visited the house to speak and interact with the students. Bruce had a strong rapport with the stu- dents, and the Crimson, the college newspaper, while nor- mally critical of the university administration, often lauclec! Bruce en c! rater! him one of the best of the house masters. During the period 1967-72 student activists often disrupted Harvarc! en c! other universities. At Harvard, the activists sought to have the university administration en c! faculty publicly denounce the United States' Vietnam policy and to bar the Reserve Officer Training Corps from the cam- pus. In the spring of 1968 a militant group occupier! the

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BRUCE CHALMERS 85 central administration burbling after ousting the college administrators. President Pusey caller! in the outside police who removed, not too gently, the occupying students. This action was met with great indignation by students en c! fac- ulty with more moderate views, as well as by the militants, en c! a college-wicle student strike was threatened. The stu clent hotly as a whole met in Harvarc! Stadium to consicler a strike. One of the few faculty members invites! to speak at this meeting, Bruce gave a conciliatory talk, en c! the strike was voter! clown. However, the college was clisruptec! for the rest of the spring term by fierce debates en c! various actions threatened by the most militant students. The extreme mili- tancy en c! unrest persistec! until the spring of 1972, when it ceasec! rather suciclenly. Throughout this period, Bruce continues! to play a mecli- ating role in reconciling the students en c! the aciministra- tion, en c! thwarting the rashest actions (e.g., torching a uni- versity builcling) attemptec! by student raclicals. His was always a moderate voice counseling the administration against harsh action towarc! the student protesters en c! trying to convince the students that their real quarrel was with the national- rather than the university administration. Also in his later years at Harvard, Bruce became espe- cially interested in the problems of energy procluction en c! conservation. Baser! on his knowlecige of soliclification mecha- nisms, he conceivec! a process for casting silicon in a single crystal ribbon form, which might be suitable for photovol- taic applications en c! which conic! be processed with mini- mal material loss. He en c! his postcloctoral fellow Tom Surek inclucec! the Mobil Tyco Corporation to sponsor research to test en c! exploit this iclea, en c! Mobil Tyco Solar Energy Corporation carrier! on such a program for several years. A number of serious clifficulties were overcome, but eventu- ally a process labeler! ecige-clefinecI, fiIm-fec! growth (EFG)

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86 BIOGRAPHICAL MEMOIRS was clevelopecI. Throughout this clevelopment Bruce playact a central role in giving acivice en c! mentoring the engineers en c! scientists working on the project. A German corporation, ASK Americas, undertook the ac- tual commercialization. Its products are hollow Si tubes with octagonal cross sections. Wafers are former! from the oc- tagonal crystal by laser cutting. Overall materials Tosses are less than S%, comparer! with 50% in the processing of bulk crystals. The company produces moclules in the form of octagons about 10 cm across each face en c! approximately 300 microns thick. Most of the moclules produce 50 watts of electricity. Currently the annual procluction is 4 megawatts of solar cell capacity, but production is being expanclec! quite rapicIly so that shortly procluction will reach some 10 megawatts per year. By the year 2000, about 20 megawatts of capacity is projected. The current cost of the finisher! product is about $4.00 per watt. The company's solar cells operate at an efficiency of 14%. Bruce en c! Ema left Winthrop House in 1973 en c! mover! to Falmouth on Cape Cod. He continued his teaching at Harvard until 1977, when he retired as professor emeritus. He kept up the consulting aireacly alluclec! to en c! playact an active part in Falmouth community affairs. In 1986, as vice- chairman of the Falmouth Tricentennial Committee, he wrote an intriguing history of the town (publisher! in the Book of Falmouth), covering the entire perioc! from the founcling of the town to 1986. His recreational activities incluclec! sail- ing, hiking, reacting, writing, photography en c! color print- ing, en c! fabrication of various objects in his home work- shop. In addition to election to the National Academy of Sci- ences (in 1975), he receiver! a number of other noteworthy honors, including a fellowship in the American Academy of Arts en c! Sciences, honorary memberships in various for

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BRUCE CHALMERS 87 eign scientific en c! technical societies, the Savour Awarc! from the American Society of Metals, en c! the CIamer Mecial of the Franklin Institute. In 1989 the Minerals, Metals, en c! Materials Society createc! the Bruce Chalmers Award, en c! Bruce was the first recipient for clistinguishec! contribu- tions to the science en c! technology of soliclification pro- cessing. In 1988 he learner! that he hac! a condition that turner! into multiple myeloma. He courageously continues! his con- sulting en c! community activities until his cleath on May 25, 1990. Ema, their five chilciren, en c! eleven grancichilciren , ~ survive mm. AM INDEBTED TO Ema and Stephen Chalmers and Alison Chalmers Rodin for supplying much personal information on Bruce's life. I thank Professor Tohn Hutchinson of Harvard University and Kalies Turis, now vice-president for research at ASK Americas, for supply ing information on the status of the silicon ribbon strip casting process. NOTES 1. B. Chalmers, professional biography. In Progress in Materials Science, Chalmers anniversary volume, ed. T. W. Christian, P. Haasen, and T. B. Massalski. Pergamon: New York, 1981. 2. Bruce Chalmers memorial minute. Harvey Brooks, William Paul, Frans Spacpen, and David Turnbull (chair), Faculty of Arts and Sciences, Harvard University, May 21, 1991. 3. W. Rosenhain. The modern science of metals, pure and ap- plied. In Science and the Nation, ed. A. C. Seward. Cambridge Univer- sity Press, 1917.

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88 BIOGRAPHICAL MEMOIRS SELECTED BIBLIOGRAPHY 1936 Micro-plasticity in crystals of tin. Proc. R. Soc. Lond. A 156:427. 1940 The mechanical effects of intercrystalline boundaries. Proc. Phys. Soc. 52:127. 1948 With R. King and R. Shuttleworth. The thermal etching of silver. Proc. R. Soc. Lond. A 193:465. 1950 With K. T. Aust. The specific energy of crystal boundaries in tin. Proc. R. Soc. Lond. A 201:210. 1953 With W. A. Tiller, K. A. Jackson, and J. W. Rutter. The redistribu- tion of solute atoms during the solidification of metals. Acta Met. 1:428. 1954 Melting and freezing. Inst. of Metals lecture. Trans. AIME. f. Met. 6:519. 1955 With C. Elbaum. The topography of solid-liquid interfaces of metal crystals growing from the melt. Can. J. Phys. 33:196. 1958 With K. A. Jackson. Freezing of liquids in porous media with special reference to frost heave in soils. 7. Appl. Phys. 29:1178. Growth of crystals of pure materials and of the solvents of solutions. In Growth and Perfection of Crystals, ed. R. Doremus, B. W. Roberts, and D. Turnbull, p. 291. New York: Wiley & Sons.

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BRUCE CHALMERS 1962 89 With P. Doherty. The origin of lineage substructure in aluminum. Trans. Met. Soc. AIME 224:1124. 1963 Structure of ingots. 7. Aust. Inst. Met. 8:255. 1964 Principles of Solidification. New York: Wiley & Sons. Interactions between particles and a solid-liquid interface. 7. Appl. Phys. 35:2987. 1965 With R. B. Williamson. Crystal multiplication without nucleation. Science 148:1717. Dynamic nucleation. In Structure, Properties, Solid Interaction, ed. T. J. Hughel, p. 308. Amsterdam: Elsevier. 1966 With D. R. Uhlmann and T. P. Seward III. The effect of magnetic fields on the structure of metal alloy castings. Trans. Met. Soc. 235:527. 1969 With M. Weins, H. Gleiter, and M. F. Ashby. Structure of high angle grain boundaries. Scripta Met. 3:601. 1971 Structure of grain boundaries. In Structure and Properties of Metal Surfaces. In honor of Professor Honda, Japan Honda Memrial Commemoration. 1972 With H. Gleiter. High angle grain boundaries. In Progress in Materi- als Science. New York: Pergamon.