Structural inhomogeneity of metallic materials and quality criteria

The object of research is the microstructure and hardness of low-alloy steel with a ferrite-pearlite structure. The research focuses on applying a multifractal approach to evaluate the relationship between microstructural features and mechanical properties, particularly hardness, under varying thermal treatment conditions. Method. Multifractal analysis was applied to steel samples subjected to thermal processing, including heating to 920 °C for 300 seconds and subsequent cooling to 500 °C over durations ranging from 29 seconds to 93 000 seconds. Structural parameters, such as the Hausdorff-Besicovitch dimension , uniformity , and dimensional coefficients (, ), were calculated to establish correlations with mechanical properties. Hardness measurements (HV) were performed to evaluate the impact of cooling time on structural evolution and mechanical performance. Results. The research revealed that increased cooling time led to a reduction in hardness, which corresponded to changes in the dimensionality of structural elements in ferrite and pearlite. Specifically, extended cooling times resulted in significant alterations to the microstructure, demonstrating a clear relationship between multifractal parameters and mechanical properties. The proposed multifractal approach proved effective in predicting hardness variations based on structural features, offering a robust tool for quality assessment and process optimization in metallurgy.