Some Studies of Metals by Means of X-Rays

Abstract

X-ray patterns of metals; (1) effect of rolling.—By passing a narrow beam of heterogeneous rays through a thin sheet of metal, a pattern may be photographically recorded which depends on the crystalline structure of the metal. The authors have used this phenomenon to study the effect of rolling and subsequent annealing on various metals. (a) In the case of aluminum, cadmium, copper, zinc, and brass, rolling produced ill-defined patterns, all with a symmetry related to the direction of rolling but each characteristic of a particular metal. (b) Silver and tin gave similar ill-defined patterns immediately after rolling, but these gradually changed during the following two or three weeks to the distinct spot patterns characteristic of annealed samples. For these metals, then, the crystal growth which accompanies annealing takes place at room temperatures. Even at 5° the recovery from rolling goes on, though more slowly (See Plate I). (c) Lead and thallium gave irregularly distributed spots which showed no symmetry related to the direction of rolling. For these metals, then, either the crystal structure is not distorted by the rolling or the recovery is quite rapid. In the case of thallium, however, the pattern was not the same as after the sheet had been annealed. (2) The effect of annealing after rolling was studied with a special furnace which enabled the patterns to be obtained for a sheet of metal kept at any desired temperature up to 800°. The various metals differ greatly in their response to annealing. Thirty minutes at 80° is sufficient to obliterate the effects of rolling in the case of silver and tin, whereas 2 hours at 800° is not sufficient for copper. The effects of annealing cadmium at 100°, 150°, 200° and 250° are shown in the photographs reproduced in Plate II. This method should be very valuable for studying the effect on metals of various mechanical and heat treatments.