The object of study is the internal and external interfaces of structural steels and alloys and products.
The subject of research is the resistance to the formation of intergranular damage and intercrystallite destruction of structural steels and alloys under the action of a force load, depending on the structural and energy state of the internal interfaces; technological modes of structure control to eliminate intercrystallite cleavage; increasing the operational reliability of products.
The aim of the work is to create scientific foundations, models and methods for controlling the structural and energy state of the interfaces of structural components when obtaining products with increased reliability parameters, taking into account the conditions of their operation.
Research methods: the general system methodology was used in the work, according to which the complex hierarchical structure of alloys was considered and investigated. The structure analysis was carried out on the basis of the concept of invariant modeling. Were used the energetic and structural-phenomenological approaches of mechanics, the essence of which is to consider the structure at various levels of the hierarchy, establish its guiding parameters and build an appropriate generalized model. The influence of the structural and energy characteristics of the internal interfaces on the properties of alloys was analyzed by methods of physical materials science. Used metallographic studies, scanning and electron microscopy, X-ray diffraction, micro-X-ray spectral and fractographic analyzes, Auger electron microscopy. Microhardness, LM-hardness were also determined, mechanical tests for tensile and impact bending were carried out at temperatures from -196 ° C to + 100 ° C. The structural-energy state of grain interfaces after ion-plasma etching of samples was assessed, system computer modeling of properties was carried out. polycrystalline alloys. Conducted research of the strength parameters of their surfaces using the open package of finite element analysis FEniCS in Python.
The structured and systematized results of the complex of experimental and theoretical studies are the scientific principles of a new approach to increasing the operational reliability of polycrystalline systems by choosing the optimal parameters of the energy state of the interfaces of the structural components.
The proposed scientific foundations and experimentally substantiated a conceptual approach to the choice of rational technologies for processing parts by using a set of system, energy and gradient models as digital twins of the interface structure to obtain products with a given life cycle.
Using the energy approach for describing continuous nonlocal media, mathematical relations are constructed for the model of polycrystalline systems. It is shown that the tendency to the formation of intergranular damage and destruction of alloys is influenced not only by the absolute values of the parameters of the properties of microvolumes, but also by their gradient.
New methodological approaches to grain-boundary design of the structure made it possible to determine the ways of controlling the structural and energy state of the interface surfaces when using the technologies of welding, heat treatment, alloying, microalloying and surface hardening, which provide an increase in the parameters of durability, resource and reliability of products while reducing the cost of their life cycle.
The criterion of intergranular strength obtained in this work is used to determine the causes of destruction of structures, as well as to optimize technologies for the manufacture of critical parts operating under conditions of intense dynamic and contact loads.
The results obtained in the dissertation can be effectively used in the selection of rational modes of welding, surface hardening, heat treatment, alloying, microalloying for the scientific substantiation of technological solutions to increase the resistance to the formation of intergranular damage and cracks in parts operating under intense external influences.
