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Commentary by

KARL T. AUST* Professor of Metallurgy University of T o r o n t o

Series Associate Editor * Professor Aust holds the Bachelor and Master of Science degrees from the Univerversity of Toronto and the Doctor of Philosophy from the same institution. He had industrial experience at U.S. Metals Refining Company, Kaiser Aluminum and Chemical Company and General Electric Company as well as research experience at Johns Hopkins University prior to joining the faculty at the University of Toronto. His research has been concerned primarily with the structure and properties of grain boundaries, annealing phenomena and their effects on the properties of metals. In 1961 (with J. W. Rutter) he received the Mathewson Gold Medal of AIME for research on the mobility of grain boundaries.

METALLURGICAL TRANSACTIONS

VOLUME 1, JULY 1970-2055

Metallurgical Classics

Kalischer and Recrystallization in the Nineteenth Century

p

RIOR tO Kalischer's research, the study of the microstructure of metals had received intermittent attention since the work of Reaumur ~) in 1722. R6aumur applied the concept of parts aggregated on different scales to explain the structures he saw on fractured metals and presented his famous drawing of the microstructure of steel. Faraday and Stodart (2) in 1820 had used etching to "develop the grain." Anossoff (a~ in 1841, Sorby "~ in 1864 and Martens ('~)in 1878 were among the early metallographers using microscopy of polished and etched samples. With regard to relevant work on the annealing of metals, Savart's study (~) in 1829 of anisotropy of elastic behaviour is said to be the first record of a change in grain structure on annealing of a cold worked metal. Bolley (7' in 1855 attempted to account for the changes in the properties and fracture behaviour of zinc on annealing in terms of allotropic changes. As early as 1858, Nogues (~) may have provided the first recorded observation of recrystallization and grain growth when he found that platinum wires heated in a reducing gas flame developed a crystalline appearance on the surface. Nogues attributed the "crystallization" of platinum to the influence of high temperatures on the "molecular state of the metal." The Percy monograph of 1864 (9) indicated that cold rolled zinc heated below the melting point shows large crystals. Percy also concluded that annealing wrought iron at high temperature would give the particles sufficient freedom of motion even below the melting point to arrange themselves in crystals. In the paper on the "Influence of Heat on the Molecular Structure of Zinc" published in 1881, Kalischer appears to have carried out the first systematic study of the effects of annealing metals following cold work. Kalischer observed that zinc sheet develops large visible grains on heating and found that this occurred only after deformation. The large grains formed on the sheet were observed visually, without a microscope, after etching with copper sulphate solution. He explained this observation by stating that the crystalline structure fo

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