SPEAKING OF MECHANISM RESPONSIBLE FOR A COMPOSITE MATERIAL MICROSTRUCTURE FORMATION UNDER WELDING OF HETEROGENEOUS COMPONENTS IN A FRICTION WITH STIRRING MODE

The problem of joint formation under friction treatment of composite materials based on immiscible components is viewed. The role of adiabatic shear bands (AShB) in the interaction with the elements forming the composite material is shown. The effects of migration of heavy low-melting components compared to adiabatic shear bands at speeds much higher than the speeds of traditional diffusion are described, making possible to take a fresh look at the possibilities of the effect of friction welding with stirring not only as an effective welding method, but also as the basis for an alternative technology for the production of alloys for immiscible components in bulk samples. It was found that the temperature in the stirring zone was high enough for intensive formation of solid solutions and intermetallic phases. The structure of such particles was formed under the influence of heating and intense plastic deformation under the conditions of the possible implementation of two mechanisms of component migration – diffusion and migration ones along AShB, reproduced with each rotation of the tool. An increase in the lead content in the composite material from 5 to 44 % led to a decrease in the coefficient of friction from 0,28 to 0,13. The main reduction in the coefficient of friction of the composite material of the Al – Pb system is achieved in the range of lead content of 0…30 wt. %. The development of the alternative technology for the production of special–purpose composite materials (CM) discussed above provides for two interrelated directions - expanding the range of new functional CM using the unique capabilities of FSW technology and clarifying the mechanism of structural and phase transformations underlying this technology. In particular, it is obvious that the mechanism and kinetics of AShB formation and their role in the formation of the microstructure and properties of composites need additional research.

friction treatment, composite material, immiscible components, adiabatic shear bands, Al–Pb system, friction coefficient.