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composition change of the surface layer


Fig. 2. (a) — Microstructure of pure iron between the A2 and A3 transformations
(cropped from border and page)

The polished specimen, presented by the two micrographs, was heated 30 minutes at 850ยบ C, i.e., just below A3. The appearance of the previously polished surface reveals the structure, which is of the same type as that prevailing at ordinary temperatures. The excessive volatilization at the margins of the grains has clearly developed the boundaries. Magnification, 500 diameters; "heat-etched"

ex Henry S. Rawdon and Howard Scott. "Microstructure of iron and steel at high temperatures." Scientific papers of the Bureau of Standards No. 356 (March 15, 1920) : 519-528
University of California copy, digitized April 4, 2007

epigram ex p 520

11 January 2014
tags: H. S. Rawdon; H. Scott; drawing; iron; metallography; structure