MERICA, PAUL DYER

(b. Warsaw, Indiana, 17 March 1889; d. Tarrytown, New York, 20 October 1957)

metallurgy

After receiving his A.B. from the University of Wisconsin in 1908, Merica taught physics in Wisconsin and “Western Subjects” in Hangchow, China, for two years before going to the University of Berlin, from which he obtained his Ph.D. in 1914. From 1914 to 1919 he was a physical metallurgist at the U.S. National Bureau of Standards, where he was involved with R. G. Waltenberg and H. Scott in research on the new alloy Duralumin, the properties of which depended on precipitation hardening—the only method of hardening metals and alloys that was not known in or before classical times.

Merica was the first to show that such hardening resulted from a change of solubility with temperature (almost unsuspected in solids at the time), and he postulated that hardening required a critical dispersion of submicroscopic particles of CuAl₂ within the matrix crystals.

This theory inspired many studies of hardening in other alloy systems, especially when it was combined with the slip-interference theory of hardening advanced by Jeffries and R. S. Archer in 1921. X-ray diffraction later showed that the greatest hardness occurred before there were detectable particles of compound, and in 1932 Merica advanced his theory of “knots,” that is, clusters with high concentration of solute atoms forming without breaking coherence with the parent lattice. The idea soon received quite independent experimental proof in the X-ray studies of Guinier and Preston. From 1919 until his death, Merica was with the International Nickel Company (director of research, 1919— 1949; president, 1949—1952). He developed several precipitation-hardening alloys of nickel, nickel-bearing cast irons, and sheet alloys for corrosion-resistant and high temperature applications.

BIBLIOGRAPHY

I. Original Works. Meriea’s most influential papers are “Heat Treatment and Constitution of Duralumin,” in Scientific Papers of the United States Bureau of Standards, 347 (1919), with R.G Wallenberg and H. Scott; repr. in Transactions of the American Institute of Mining and Metallurgical Engineers, 64 (1920), 41–79; and “The Age-Hardening of Metals,” ibid., 99 (1932), 13–54.

II. Secondary Literature. For a complete list of Mericsa’s publications and further biographical information, see Z. Jeffries, “Paul Dyer Merica’s in Biographical Memoirs, National Academy of Sciences, 33 (1959), 226–239

For a review of the history of precipitation-hardening, see H. Y. Hunsicker and H. C. Stumpf, “Historv of Precipitation Hardening,” in C. S. Smith, ed., The Sorby Centennial Symposium on the History of Metallurgy (New York, 1965), 271–311.

Cyril Stanley Smith