Microstructure, Strength, and Fracture Topography Relations in AISI 316L Stainless Steel, as Seen through a Fractal Approach and the Hall-Petch Law

Abstract

The influence of the fracture surface fractal dimension D F and the fractal dimension of grain microstructure D M on the strength of AISI 316L type austenitic stainless steel through the Hall-Petch relation has been studied. The change in complexity experimented by the net of grains, as measured by D M , is translated into the respective fracture surface irregularity through D F , in such a way that the higher the grain size (lower D M values) the lower the fracture surface roughness (lower values of D F ) and the shallower the dimples on the fractured surfaces. The material was heat-treated at 904, 1010, 1095, and 1194°C, in order to develop equiaxed grain microstructures and then fractured by tension at room temperature. The fracture surfaces were analyzed with a scanning electron microscope, D F was determined using the slit-island method, and the values of D M were taken from the literature. The relation between grain size, D M , mechanical properties, and D F , developed for AISI 316L steel, could be generalized and therefore applied to most of the common micrograined metal alloys currently used in many key engineering areas.