Materials Science: Parepistemes Rampant
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behavior (explanation of discontinuous yield and strain-aging in steels), randomwalk theory applied to diffusion and later also to rubberlike elastidty, band theory of conduction in solids, cohesion of solids viewed in quantum-mechanical terms, and theory of color centers in ionic crystals. It is instructive to consider the attitudes of metallurgists and physidsts to dislocations. Many metallurgists were fiercely resistant; they thought the dislocation, postulated in 1934, an unnecessary hypothesis—and it was a hypothesis only, since its reality was not demonstrated unfil the end of the 1940s. Among physidsts there were positivists, like Percy Bridgman, who did not take an interest in dislocations. Most in This article is based on a plenary address which Robert W. Cahn, Cambridge University, delivered bofh camps, however, were convinced by at the International Union of Materials Research Societies International Conference on Advanced the rigorous quantitative treatment, espeMaterials (IUMRS-ICAM'99) hosted by the Chinese Materials Research Society (C-MRS) in Beijing, on June 14,1999. A Version ofthis article is also being published in Materials Today, the dally by Alan Cottrell. A particularly conquarterly magazine published by Elsevierfor the European-MRS. A report ofthe IUMRS-ICAM'99 vincing example of the power of the strictly quantitative approach was J.L. Snoek's meeting will be published in afuture issue o/MRS Bulletin. linkage, 1939-1941, of internal friction in wires of iron containing dissolved carbon science as distinct from a craft, scarcely Disdplines emerge either by the fission or nitrogen to the solute concentration. goes back before the middle of the 19th or the fusion of older disdplines. The reaThat linkage allowed minute interstitial Century. The fusion of metallurgy and son for such emergence may be profound concentrations to be measured by purely or eise trivial. Fission is the more common: solid-state physics came about because of physical means. This marked the beginperceived educational needs in the late thus, physical chemistry was created and ning of this century's conversion of compo1950s, and that fusion was cemented by split resolutely from organic chemistry in sitional analysis of materials from a chemi the invention of the Materials Research the 1880s because of the founders' passion cal into a physical skill. Laboratories in the United States in the to establish generalizations about reaction 1960s. The rearguard fight of those who equilibria and kinetics as distinct from coldid not want to be fused was long and bit lecting facts about particular reactions. ter; great research metallurgists such as That was a profound event. Chemical I have just used the Robert Mehl fought hard against these physics split from physical chemistry in word parepisteme, which developments but they were defeated in the 1930s mainly because of many people's I have invented to denote a the end. Others, in the first half of the 20th exasperation with a physical chemist who Century, poured comprehensive sco
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