SURFACE FORMATION ENERGY FOR INTERGRANULAR FRACTURE IN 2-DIMENSIONAL POLYCRYSTALS

A global energy minimization method for calculating intergranular frac ture surfaces which minimize surface formation energy was developed us ing standard graph algorithms, The intergranular fracture of equiaxed, single-phase, polycrystalline grain structures was examined under a v ariety of energetic conditions. In energetically isotropic systems the minimum energy fracture surface has length 1.1 times the sample width independent of grain size, A criterion for fracture mode was derived for this case. Using a ball-and-spring model, local mechanical effects were found to increase fracture length by at most 5% in isotropic sys tems, The presence of typical low-energy, low-angle grain boundaries m inimally affects intergranular fracture path, but may alter the prefer red fracture mode, In systems with randomly dispersed, very weak bound aries (i.e., micro-cracks), fracture surfaces veer to follow low surfa ce formation energy boundaries, resulting in tortuous, low-energy frac ture paths, and intergranular fracture is strongly preferred.