Applications of X-ray Diffraction to Metallurgical Science

Abstract

At the time of the discovery of X-ray diffraction, the knowledge of the structure of metals was limited to what could be revealed by optical microscopy. From the occasional occurrence of metallic crystals with well defined plane faces, it was recognized that the structure of metals was essentially crystalline. Little but speculation existed as to the actual atomic arrangement, although the geometrical theory of space-groups and space-lattices had been laid down long before the detailed atomic arrangement could be determined. The general principles of metallic phase diagrams had been established by Roozeboom and others, and the experimental work of Heycock and Neville (1897) had shown how the limits of the different phase fields could be established. to a high degree of accuracy, even in very complicated systems. At the same time the German School under Tammann had produced a rapid survey of a number of metallic equilibrium diagrams, but the underlying structures remained a mystery. The application of microscopical methods to the study of steels had resulted in the recognition of a number of 'constituents,' but confusion often existed as to whether these were distinct phases with definite crystal structures, or were mixtures of phases on a scale too fine to be resolved by optical methods. The general position was, therefore, one in which further progress depended on the discovery of some method by which the detailed atomic arrangement in metals could be revealed.