Superplasticity of nickel-based alloys with micro- and sub-microcrystalline structures

摘要

This paper will describe the generation of micro- and sub-microcrystalline structures in two Ni-based alloys that are typically strengthened by phases, such as γ' and γ"+δ. The relationship between the superplastic behavior and microstructure will be discussed. High strain deformation processing in the temperature range of 0.9T{sub}m to 0.6T{sub}m results in reduction of the initial coarse-grained structure (>100 μm) to a range of structures including microcrystalline (MC) (grain size <10 pm) and sub-microcrystalline (SMC) (grain size <1 μm) with increasing deformation. The influence of alloy chemistry and constituent phases on dynamic and static recrystallization is considered, and their effect on grain refinement is described. Low-temperature and high strain rate superplasticity can be observed in dispersion-strengthened alloys with SMC structures. It was established that in dispersion-hardened Ni alloys with SMC structures, superplasticity can be observed at temperatures 200-250°C lower than in alloys with MC structure.