ION-INDUCED PHASE-TRANSFORMATION IN TYPE-304 AUSTENITIC STAINLESS-STEEL BY RARE-GAS ION IRRADIATION

Foil specimens of austenitic stainless steel (type 304 stainless steel) were irradiated with 50- 400 keV Ar, Kr, and Xe ions in the fluence range of 1×1020-1×1021 ions/m2 at room temperature. It has been shown by glancing angle x-ray diffraction (GXRD) measurement that the amount of ion-induced phase transformation of γ →α' in the foil specimens depends strongly on irradiation conditions such as ion species, energy, and fluence; the amount of the phase transformation at saturation increases linearly with increasing ion range. An ion-induced new peak was found in the GXRD pattern, which is shown to be due to solidification of implanted rare-gas atoms in the stainless steel. The solid phase inclusions of the rare-gas atoms have a close correlation with the phase transformation. It is shown that the phase transformation is induced by the formation of highly pressurized rare-gas inclusions, while the formation of the inclusions depends on a depth distribution of implanted rare-gas atoms.