The hard and soft states in ductile metals

Abstract

In connection with the previous research attempts were made to break down the crystalline structure of the metal as completely as possible by wire drawing. On etching the surface of wires prepared in this way the structure disclosed appeared to be finely granular, no traces of crystalline grains or of patches of uniform orientation being visible. After the publication of the former paper the wires which had been then used were subjected to a more searching examination. Specimens were ground so as to expose longitudinal sections at various depths and these were etched till the true understructure was disclosed. At low magnifications the structure appeared to consist of parallel strands or fibres which became thinner and either pinched out or drew closer together at the point of fracture. The general character of this structure is shown on fig. 1, which is a diagrammatic sketch of the fractured end of a hard-drawn gold wire. For the proper resolution of the intimate structure of these strands or fibres, a lens of fairly high N. A. is necessary, and in the photomicrographs, figs. 2 and 3, a 4-mm. objective of 0·95 N. A. was found most suitable.