Formation of Nanocrystalline Structure Upon Severe Thermomechanical Processing and Its Effect on the Superplastic Properties of Nickel Base Alloys

Abstract

This paper is the systematic study of the mechanisms of structure formation of a wide range of nickel and nickel-iron based alloys with different types of strengthening (y+y'; y+5+y"; Y+y'+Y 20 3) in a wide temperature -strain rate interval of plastic deformation. Regimes of thermomechanical processing that provide stage-by-stage transformation of a coarse-grain structure into a microcrystalline (MC) one, and further to nanocrystalline (NC) structural state, have been established. The regularities of the effect exerted by the morphology of strengthening phase and processing conditions on the development of structure formation during hot, warm and cold deformation have been revealed. The correlation between the phase composition and the type of strengthening of superalloys with thermal stability of SMC and NC structures, and the possibility of manifestation of the effects of low temperature and high strain rate superplasticity (SP) have been revealed.