The insides of metals

SEP 01, 1950

The microscopic examination of fractured metal by a special “fractographic” technique is proving useful in revealing something of the manner in which metal coheres and in throwing some light on the nature of the minute subdivisions of metallic crystals.

DOI: 10.1063/1.3066993

Carl A. Zapffe

Lost in antiquity are the origins of many methods used for examining metals, but the epochal discovery of the optical microscope a few hundred years ago originated the study of metals at high magnification. In its early stages, investigation with the microscope was limited to an exploration of surfaces. This was uninstructive because the principal service of metals lies in their strength, hence, in their internal constitution. The French scientist de Réaumur in 1722 and Sweden’s Swedenborg in 1734 advanced the application of the microscope somewhat by studying the surfaces of fractures of metals, which disclosed some information regarding the manner in which metals are constituted. However, the difficulty of bringing the microscope lens close to the jagged surface of a fracture discouraged, for more than two centuries, these and all later scientists from developing such an application.

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Carl A. Zapffe, Batelle Memorial Institute.