REGULARITIES OF STRUCTURAL CHANGES AFTER FRICTION STIR PROCESSING IN MATERIALS OBTAINED BY THE ADDITIVE METHOD

摘要

Nowadays the technologies of obtaining metal materials by additive methods are becoming more and more pertinent. Such technologies may differ from one another by the type of heat source responsible for the material melting in the printing area. By this classification, the techniques are divided into electric arc, laser-, and electron-beam additive processes. According to the method of material feeding to the printing area, metal additive manufacturing technologies are divided into powder and wire technologies. Among the technologies based on direct material feeding into the melting zone, the best results are achieved by wire-feed electron-beam technology with regard to the quality of the material obtained in printing. In this case, in the conditions of electron-beam additive manufacturing of components, the coarse crystalline structure of samples is formed, with a directed growth of dendrites towards heat dissipation, which creates both the possibility of additional use of such features and disadvantages as a material strength at the level of the cast softened structure. Also, in the process of obtaining polymetallic products there is the formation of heterogeneity, which causes a decrease in mechanical or operational properties of the final product. In turn, the method of friction stir processing is widely known as a method of the local structure modification and hardening the material by forming a stir zone with a submicrocrystalline or ultrafine grain structure. To study the possibility of hardening of materials obtained by the electron-beam additive manufacturing method, as well as the removal of defects from products, the structure and mechanical properties of polymetallic materials samples of Cu-Fe system, obtained by the additive manufacturing method and processed by friction stir processing have been studied in this work. Combination of the above-mentioned technologies in the work allowed forming samples of composite structure, with alternation of layers differing by the size of iron particles in the copper matrix, as well as forming samples with more uniform distribution of components structure in the system, which cannot be achieved separately by the additive electron-beam technology. The average grain size in the most finely dispersed layers of samples was less than 250 nm.