Basis of quantitative metallography PDF

INTRODUCTION \

Until fairly recently, optical metallography has been essentially qualitative in nature, but has been successful in accounting for relatively large scale differences in the mechanical properties of metals and alloys. The technique has also been useful in allowing the effects of processing to be studied in terms of microstructural changes. Over the past 15 years however, there has been a marked change, largely because of the realisation that the properties of metals and alloys not only are dependent on the quality of their microstructures, but also may be quite rigorously related to the quantitative aspects of the amount, size shape and distribution of the phases present in the structure. The efforts of Gensamer in relating the tensile properties of pearlitic steels to the pearlite interlamellar spacing, and those of tempered martensite to the mean free path between carbides, together with the wide applicability of the Hall-Petch relationship between grain size and yield or flow stress has led to it being accepted that it is necessary to describe microstructures in very quantitative terms. This approach, a study of which was undertaken about 30 years ago in order to determine isothermal transformation diagrams and Ms temperatures more accurately, has now been widely employed in the physical metallurgy of steels and non-ferrous alloys.

Edited by: F. B. Pickering