The Geometric Compatibility Factor Determining Brittle Crack Propagation Across Boundary in Bainitic Low Alloy Steels

Abstract

Boundary properties between two adjacent grains with different crystallographic orientation relation are important factors in deciding the mechanical properties of materials. in our previous reports, we introduced the geometric compatibility equation as a factor determining the brittle crack propagation condition into the adjacent grain in banitic low alloy steel as follows:M = cos α · cos θwhere α is the angle between crack normal in the cracked grain-I and normal to (001) plane in the adjacent grain-II and θ is the angle between normal to (001) plane in the grain II and loading axis.(see FIG. 1) Higher M gives greater possibility to the crack propagation. The geometric compatibility factor (M) could be easily calculated from the crystallographic data obtained from Electron Backscatter Diffraction (EBSD) analysis, and successfully predicted actual crack propagation plane. We also found that there was a critical M value to arrest the brittle crack propagation at the boundaries.