Techniques for the study of micro-phases and their influence on material properties

Abstract

In modern materials research the necessity of studying processes in great detail requires the application of special techniques. Several advanced techniques are available for the study of micro-phases and their influence on material properties. Specific information from each technique enables comprehensive data to be obtained. Various techniques and equipment are briefly described. Electron microscopy is used for the study of fine-scale structural details and electron microfractography for the investigation of failure initiation, mode of failure and the influence of minor constituents. Elegant extraction replica techniques are available for the study of precipitates and electron and X-ray diffraction is used for their identification. Thin foil techniques provide a quantitative approach and a three dimension structural picture. The use of heating, straining and cooling stages in the electron microscope allows events to be followed as they occur and to be recorded by sequential and cine-photography. Electron probe X-ray microanalysis is used for the study of solution segregation problems, diffusion couples, composition of oxide films, non-metallic inclusions, precipitates, precipitate and nucleation processes, grain boundary and denudation effects etc. Potentially powerful new techniques such as the application of probe analysis to the light elements and ion-beam micro-analysis for the identification of isotopes are being developed. New developments such as emission electron microscopy for observing solid surfaces and extending the range of hot-stage microsopy to the electron optical range and the study of temperature-dependent changes as they occur are being assessed. The potential advantage of the development of new equipment such as the combination of scanning, transmission electron microscopy and probe analysis in one instrument is discussed. The paper reviews, with a comprehensive list of references to published work, the techniques for study of fine-scale physical processes in metals. The advantages of several techniques are discussed and illustrated by relevant work NEL. This includes studies of the effect of N in Al and Si killed steels, negative creep, structural changes in creep vacuum melting reduction of impurities in ball bearing materials, tin oxide problem in bearings and H embrittlement, etc. (Mr. D. Scott, Head, Metallurgy Section, National Engineering Laboratory, D.S.I.R., England)