(b. Berlin, Germany, 24 August 1875; d. Kingston Hill, Surrey, England, 17 March 1934)
Rosenhain was the son of Moritz Rosenhain, a businessman. His mother was the daughter of a rabbi. The family immigrated to Australia in 1880 so that the son would not have to serve in the Prussian military. After attending Wesley College, Melbourne, and then Queen’s College, Melbourne University (1892–1897), where he received the bachelor of civil engineering, Rosenhain went on to Cambridge University as 1851 Exhibition scholar (1897–1900). He received the D.Sc. from Melbourne in 1909. A fellow of the Royal Society (1913), Rosenhain was also a founder-member, president, and fellow of the Institute of Metals and Carnegie and Bessemer medalist of the Iron and Steel Institute. At Cambridge, Rosenhain studied under James Alfred Ewing, professor of mechanics. Initially he was assigned to a project concerning the dynamics of steam jets. This problem proved uncongenial, and in November 1898 Rosenhain abandoned it to undertake an investigation, suggested by Ewing, that was to shape his career.
Rosenhain applied the micrographic technique pioneered by Henry Sorby to a study of metal strips that had been polished and then deformed. In this way he discovered slip lines, which indicate that plastic deformation has taken place by the sliding of crystalline lamellae over each other. This discovery, which formed the subject of the Bakerian lecture in 1899, was of major importance for two reasons: it confirmed, thirteen years before the advent of X-ray diffraction, that metals consist of crystalline grains (an opinion still contested at that time); and it showed how plastic deformation, the most useful distinguishing mark of the metallic state, is possible without disruption of crystalline order. This research led Rosenhain to specialize in metallurgy and created his enduring reliance on microscopic techniques.
In 1900 Rosenhain left Cambridge. No opening in metallurgical industry was available, and he accepted a post with Chance Brothers Ltd., a Smethwick glass-manufacturing firm. He described himself as “a tame scientist kept on the premises.”1; His engineering knowledge also found extensive application, however, and he retained a permanent interest in the technology of glass. His experiences led him to the study of refractory crucible materials of high purity. While continuing research in a private metallurgical laboratory Rosenhain first adopted George Beilby’s hypothesis that a thin metallic layer between slip lamellae is reduced to the amorphous state; this layer was taken to be very hard, like glass, thus explaining the mystery of work-hardening during plastic deformation. (Recovery of work-hardened metal was attributed to crystallization of the amorphous layer.)
Rosenhain soon extrapolated this notion to form the hypothesis that the boundaries between metal grains consist of thin (liquidlike) amorphous layers that, by analogy with work-hardened metal, he believed to be very hard at low temperatures but so soft at high temperatures as to favor intergranular rupture. Later he came to believe that the hardening of steel is due to the presence in quenched steel of amorphous layers that (by analogy with work-hardened metal) he took to be very hard at low temperatures. This complex of ideas, the “amorphous hypothesis,” became the scientific mainspring of Rosenhain’s standpoint and he devoted his exceptional powers as a controversialist to its defense. Modern techniques of X-ray diffraction and electron microscopy, used to establish the nature of hardened steel and the role of dislocations in plastic deformation, have proved the amorphous hypothesis wrong in all three of its aspects. But Rosenhain’s impassioned advocacy of the hypothesis did lead him to undertake valuable experimental work, particularly on plastic deformation.
A particularly informative account of the “β-iron controversy,” concerning the basic mechanism of the hardening of steel and including an account of Rosenhain’s early role in it, was published by Morris Cohen and James M. Harris.2 (Before conceiving the amorphous interpretation, Rosenhain was a firm defender of the fallacious β-iron theory of hardening.)
In 1906 Rosenhain was offered the post of superintendent of the recently established department of metallurgy and metallurgical chemistry at the National Physical Laboratory, Teddington. Rosenhain accepted the post, considering it a stepping-stone3 to better things, but he became absorbed by the work and remained there for twenty-five years. Under Rosenhain it became one of the world’s largest and most renowned metallurgical laboratories.
When Rosenhain arrived at Teddington, metallurgy (as the department’s quondam name illustrates) was virtually a branch of chemistry. Rosenhain steered metallurgy in the direction of physics, and through his influence the new science of physical metallurgy emerged. His 1914 book Introduction to Physical Metallurgy was widely influential. This reorientation of the aims and methods of metallurgy was essential to rapid progress in the understanding of the structure and behavior of metals and alloys. Rosenhain, trained as an engineer, maintained close connections with the metallurgical industry; for him, the later separation of advanced metallurgical science and technology would have been unthinkable. His industrial outlook and connections enabled him to leave Teddington in 1931, before compulsory retirement from the civil service, to become a free-lance metallurgical consultant in London.
In 1923 Rosenhain toured American industrial and academic metallurgical installations, and his series of eleven articles in Engineer provides an expert impression of American metallurgy at that time.4
At Teddington, Rosenhain participated especially in the development of instruments for physical metallurgical research, such as his gradient furnace and the plotting thermograph for registering thermal anomalies during the cooling of alloys.5 He also improved the metallurgical microscope and invented a recording dilatometer. He directed a long series of researches on the constitution of steels and on the constitution and age-hardening of aluminum alloys, which included the important aluminum-nickel-magnesium alloy known as “Y alloy.” Rosenhain established new standards of accuracy, paying particular attention to the purity of the constituent metals and—equally important—of the refractories used for making the melting crucibles. He also studied copper alloys and dental amalgams (the first instance of subzero metallography). He was one of the first to study the regularities governing the properties of series of solid solutions. Rosenhain influenced metallurgy both as an experimentalist and as a catalyst for the work of others. During a period when the conceptual basis of quantitative treatment of problems in physical metallurgy was not yet available, he contributed little of permanent importance as a theorist, except as a forceful controversialist who spurred others to fruitful attempts to prove him wrong.
1. The source of this information is an unpublished biographical MS prepared by Mrs. Nancy Kirsner of Melbourne, Rosenhain’s daughter, who kindly placed it at the writer’s disposal, together with supplementary comments by the late Daniel Hanson, Rosenhain’s senior collaborator in his second decade at the National Physical Laboratory.
2.Sorbs Centennial Symposium, 209–233.
3. Kirsner, op. cit.
4. Rosenhain for some years edited and frequently contributed anonymously to a special supplement, entitled Metallurgist, of the journal Engineer.
5. Rosenhain, “Some Methods of Research in Physical Metallurgy,” in Journal of the Institute of Metals (1929).
I. Original Works. A complete bibliography of books, papers, and occasional articles by Rosenhain is in John Haughton’s obituary of him (see below), 28–32. His more important or characteristic publications include “The Crystalline Structure of Metals,” in Philosophical Transactions of the Royal Society, 193A (1900), 353–375, written with J. A. Ewing; Glass Manufacture (London, 1908); “The Crystalline Structure of Iron at High Temperatures,” in Proceedings of the Royal Society, 83A (1909), 200–209, written with J. C. Humfrey; “The Fatigue and Crystallization of Metals,” in Journal of the West of Scotland Iron and Steel Institute, 16 (1909), 129–146; “Metallographic Investigations of Alloys,” in Journal of the Institute of Metals, 1 (1909), 200–226; “Ninth Report to the Alloys Research Committee on the Properties of Some Alloys of Copper, Aluminium and Manganese,” in Proceedings of the Institution of Mechanical Engineers (1910), 119–292, written with F. C. Lantsberry; “The Constitution of the Alloys of Aluminium and Zinc,” in Philosophical Transactions of the Royal Society, 211A (1911), 315–343, written with S. L. Archbutt; “The Intercrystalline Cohesion of Metals,” in Journal of the Institute of Metals, 10 (1913), 119–139, written with D. Ewen; “The Tenacity, Deformation, and Fracture of Soft Steel at High Temperatures,” in Journal of the Iron and Steel Institute, 87 (1913), 219–271, written with J. C. Humfrey; An Introduction to Physical Metallurgy (London, 1914); and “Some Appliances for Metallographic Research,” in Journal of the Institute of Metals, 13 (1915), 160–183.
Later works are “Aluminium and Its Alloys,” in Journal of the Royal Society of Arts, 68 (1920), 791–798, 805–817, 819–827; Eleventh Report to the Alloys Research Committee on Some Alloys of Aluminium (London, 1921), summarized in Proceedings of the Institution of Mechanical Engineers (1921), 699–725, written with S. L. Archbutt and D. Hanson; “The Hardness of Solid Solutions,” in Proceedings of the Royal Society, 99A (1921), 196–202; “The Inner Structure of Alloys,” in Journal of the Institute of Metals, 30 (1923), 3–26; “Science and Industry in America,” in Engineer, 136 (1923), 270–271, 298–299, 312, 330–331, 358–359, 384–385, 412–413, 440–441, 468–469, 494–496, 522–524; “Solid Solutions,” in Transactions of the American Institute of Mining and Metallurgical Engineers, 69 (1923), 1003–1034; “The Present Position of the Amorphous Theory,” in Metallurgist, 1 (1925), 2–4; “The Metallography of Solid Mercury and Amalgams,” in Proceedings of the Royal Society, 113A (1926), 1–6, written with A. J. Murphy; “Presidential Address,” in Journal of the Institute of Metals, 39 (1928), 27–51; “Some Methods of Research in Physical Metallurgy,” ibid., 42 (1929), 31–68; “The Development of Materials for Aircraft Purposes,” in Journal of the Royal Aeronautical Society, 34 (1930), 631–642; and “Physik und Metallkunde,” in Zeitschrift für Metallkunde, 22 (1930), 73–78.
II. Secondary Literature. See Cecil Desch, in Obituary Notices of Fellows of the Royal Society of London, 1 (1932–1935), 353–359; Daniel Hanson, in Journal of the Institute of Metals, 54 (1934), 313–315; and John Haughton, “The Work of Walter Rosenhain,” ibid., 55 (1934), 17–32, with full bibliography. See also C. S. Smith, ed., The Sorby Centennial Symposium on the History of Metallurgy (New York, 1965), 221–222, 317–320.
R. W. Cahn