Study of the lineage structure of building steel by atomic force microscopy

Abstract

The paper presents the results of a comprehensive study of micro-and nanostructures of steel by optical and atomic force microscopy methods, carried out in accordance with international standards. The studies were carried out on samples healed in two different ways: complete quenching and quenching from the intercritical interval. The object of the study was structural alloyed building steel 1.0481 with troost-martensitic and ferritic-martensitic structures. The chemical composition of the steel was controlled using method of optical emission spectrometer (Q8 MAGELLAN). Sample preparation for AFM investigations did not include etching. Microstructure studies were performed on optical microscopes Metam RV-22 and Neophot-21. Optical microscopy showed the presence of steel hardened from the intercritical interval in the structure of the sample, and a stitch structure consisting of ferrite and martensite. A quantitative assessment of the hardening phase (martensite) was carried out using the KOI-1 program, intended for the quantitative metallographic analysis of digital photographs of the microstructure of materials. According to stereometric analysis of the microstructure of this sample, the volume fraction of ferrite is 70 %. Three-dimensional images of the surface of the samples were obtained by atomic force microscopy (PHYWE Compact AFM) in the tapping mode in an air atmosphere. Next, one-dimensional (texture, roughness, waviness) and statistical parameters of the surface topography (arithmetic average roughness, root mean square roughness, asymmetry, excess) were determined. The method of counting cubes was used to estimate the fractal dimension. A comparative analysis of the data showed that a surface with a stitch structure is more developed and has higher roughness parameters and fractal dimension values than a surface with a homogeneous structure of troost-martensite.

Relationship between the Structural-Phase Composition and the Fracture Mechanism of High-Strength Contruction Steel

“…3, b). The dimensions of shear facets match the dimensions of martensitic layers, which is correlated with the data reported in [10][11][12]. Also, individual secondary open cracks can be seen on the fracture that indicate cracking in the direction perpendicular to the main plane of the fracture (Fig.…”