Evaluation of Local Thickness and the Lineal Intercept Method as Grain Size Metrics

Author(s):

Bobby C Kaman, Daniel O Lewis, James D Paramore, and Brady G Butler

Abstract:

Microstructure analysis is an essential part of any attempt to describe a material; many engineering materials’ particular properties can be attributed their specific microstructural features rather than their bulk composition. Grain size distributions and their centrality measurements are commonly used to describe the scale of microstructural features. The lineal intercept method is a standard grain-size metric that returns either a mean grain size or grain size distribution (depending on the specific application of the method). Here, this method is compared with “local thickness” distributions of a microstructure. This distribution describes the size of the largest circle that can be inscribed at every pixel. It is an area-weighted measurement and describes something fundamentally different about the shapes but is found to be proportional for equiaxed microstructures. Definitions are given and strengths, weaknesses, and caveats are discussed for each method. Distributions are directly compared for single- and multi-mode grain size distributions generated from Voronoi diagrams. The sensitivity of each method to poor image segmentation is also explored.