Advances in Physical Metallurgy and Processing of Steels. Microstructural Evolutions with Precipitation of Carbides in Steels.

Abstract

The studies on the crystallographic features of diffusional transformation of austenite in various steels have been reviewed. A primary ferrite forming at an austenite grain boundary is related to at least one of the austenite grains separated by the boundary with the Bain correspondence. In the case of the microstructures containing both ferrite and carbides such as pearlite, degenerate pearlite, interphase precipitation of alloy carbides, and upper and lower bainites, the crystallographic relationships between ferrite and carbides provide further information to elucidate the transformation mechanisms. In the present report, therefore, the orientation relationships between ferrite, carbide and austenite as well as the habit planes of platelike transformation products and the mechanisms of transformations are discussed.