Microstructural models for quantitative analysis of grains and second-phase particles

Abstract

Microstructural models for quantitative analysis of shapes and orientationsof grains and second-phase particles on plane sections have been proposed. The models use rectangle, ellipse, regular, and elongated polygons as idealized shapes. For each shape, a function describing the change of average linear intercept length with the scan angle has been derived. These functions are used in the identification of individual shapes as well as in the quantitative characterization of the collection of two-dimensional objects such as grains and particles. In addition, the shape index proposed in the author's earlier work has now been extended to describe the conglomerates of grains or second phase particles. A new orientation factor describing an object's alignment has also been proposed. A simple method for constructing the normalized average intercept length versus scan angle plots using polar coordinates is also presented. The utility of the proposed methodology is illustrated in an example of the characterization of the size, shape, and degree of orientation of subgrains in the 7050 aluminum alloy.