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1 Merica, Paul Dyer
SUBJECT AREA: Metallurgy[br]b. 17 March 1889 Warsaw, Indiana, USAd. 20 October 1957 Tarrytown, New York, USA[br]American physical metallurgist who elucidated the mechanism of the age-hardening of alloys.[br]Merica graduated from the University of Wisconsin in 1908. Before proceeding to the University of Berlin, he spent some time teaching in Wisconsin and in China. He obtained his doctorate in Berlin in 1914, and in that year he joined the US National Bureau of Standards (NBS) in Washington. During his five years there, he investigated the causes of the phenomenon of age-hardening of the important new alloy of aluminium, Duralumin.This phenomenon had been discovered not long before by Dr Alfred Wilm, a German research metallurgist. During the early years of the twentieth century, Wilm had been seeking a suitable light alloy for making cartridge cases for the Prussian government. In the autumn of 1909 he heated and quenched an aluminium alloy containing 3.5 per cent copper and 0.5 per cent magnesium and found its properties unremarkable. He happened to test it again some days later and was impressed to find its hardness and strength were much improved: Wilm had accidentally discovered age-hardening. He patented the alloy, but he made his rights over to Durener Metallwerke, who marketed it as Duralumin. This light and strong alloy was taken up by aircraft makers during the First World War, first for Zeppelins and then for other aircraft.Although age-hardened alloys found important uses, the explanation of the phenomenon eluded metallurgists until in 1919 Merica and his colleagues at the NBS gave the first rational explanation of age-hardening in light alloys. When these alloys were heated to temperatures near their melting points, the alloying constituents were taken into solution by the matrix. Quenching retained the alloying metals in supersaturated solid solution. At room temperature very small crystals of various intermetallic compounds were precipitated and, by inserting themselves in the aluminium lattice, had the effect of increasing the hardness and strength of the alloy. Merica's theory stimulated an intensive study of hardening and the mechanism that brought it about, with important consequences for the development of new alloys with special properties.In 1919 Merica joined the International Nickel Company as Director of Research, a post he held for thirty years and followed by a three-year period as President. He remained in association with the company until his death.[br]Bibliography1919, "Heat treatment and constitution of Duralumin", Sci. Papers, US Bureau of Standards, no. 37; 1932, "The age-hardening of metals", Transactions of the American Institution of Min. Metal 99:13–54 (his two most important papers).Further ReadingZ.Jeffries, 1959, "Paul Dyer Merica", Biographical Memoirs of the National Academy of Science 33:226–39 (contains a list of Merica's publications and biographical details).LRD -
2 Metallurgy
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