The Tensile Properties of Single Iron Crystals

Abstract

AT the autumn meeting of the Iron and Steel Institute held in Birmingham on September 9-11, Prof. C. A. Edwards and Mr. L. B. Pfeil presented a continuation of their work on the subject of the tensile properties of single 'iron crystals. Eighteen months ago, they succeeded in preparing some large iron crystals by the method of straining and heating introduced by Carpenter and Elam. The large crystals described in the present paper were prepared by this method, although some small modifications have been introduced which allow them to be made with greater certainty. This method consists, briefly, in so treating the original mild steel sheets as to obtain a grain size of 120 per square mm. Suitable strips were decarburised at 875° C. for 48 hours, heated to 1000° C. for 12 hours, and finally slowly cooled. In this way a number of strips 8 in. × 1½ in. × 1/8 in. were obtained, each strip consisting of one large crystal in the central part. In all cases it was necessary to remove the surface film of fine crystals by carefully filing before the existence of the large crystals could be detected by light etching. Test-pieces were cut from these with the aid of a manganese templet. This ensured that they were all of the same size and minimised the risk of bending of the metal, which is very soft. The test-pieces were 2.5 in. × 0.75 in. × 0.110 in.