Fabrication of nanostructure in inner-surface of AISI 304 stainless steel pipe with surface plastic deformation

In the present investigation, a pipe inner-surface grinding (PISG) technique was developed to fabricate nanostructure in the inner-surface of an austenitic 304 stainless steel pipe. PISG was performed by high speed shearing with hard sphere tips, leading to gradient distribution of strain, strain rate and strain gradient along depth. Nano-austenite with an average boundary spacing of 20 nm was generated, followed by deformation microstructure characterized by shear bands, multi- and uni-directional twins and planar dislocation arrays. Deformation induced grain refinement of austenitic 304 stainless steel with low stacking fault energy (SFE) covering 4-5 order's magnitude of length scales toward nanometer regime was unified.