Influence of deformation degree at cold drawing on structure-properties relationship of a Fe-Ni-Cr superalloy

Abstract

Cold deformation is effective in significantly improving the strength of engineering materials while avoiding surface oxidation caused by hot deformation. However, the underlying mechanisms of cold deformation impacting the mechanical properties of superalloys remain ambiguous. In this study, a Fe-Ni-Cr superalloy was pre-strained to various degrees by cold drawing to investigate the effect of cold deformation on its microstructure and mechanical properties. The initial non-textured microstructure before deformation is observed to gradually transform into< 111 > and< 100 > fiber textures by the application of pre-strains. Detailed X-ray diffraction and transmission electron microscopy reveal that the deformation mechanisms transform from dislocation slip at low pre-strains (<0.47) to nanotwinning at high pre-strains (>0.47). A novel twinning-detwinning process at high pre-strains was identified to be responsible for the achieved good combination of an ultra-high yield strength of 967 MPa and a reasonable elongation of 12 % for the studied alloy. The mechanism and corresponding impacts of cold deformation on mechanical properties identified in this study can serve as a crucial step in designing ultra-high-performance superalloys.