Investigation of the fracture structure of a composite material after bending test by atomic force microscopy

Abstract

Abstract The paper presents the results of a study of the surface fracture tested for bending at negative temperatures of a ferrite-martensite composite (FMC) obtained on the basis of K 02704 structural hypoeutectoid steel by atomic force microscopy. Metallographic studies of the sample were carried out on longitudinal sections. Investigations of microstructures were performed on optical microscopes Metam RV-22 and Neophot-21. Impact bending tests were carried out in accordance with ISO 148-1:2016. The quantitative assessment of martensite was carried out using the digital imaging program and amounted to 30%. A three-dimensional image of the fracture of the sample surface was obtained by atomic force microscopy (Nanoeducator II) in the semi-contact mode. An AFM study of the fracture surface showed that the data of optical and atomic force microscopy are in agreement. The three-dimensional AFM image of the surface fracture and its profiles, extracted in different areas, as well as the roughness parameters, show the presence of a dual line structure in steel.