Irradiation effect of rare-gas ions in type 304 austenitic stainless steel

Abstract

Ar, Kr and Xe rare-gas ions were irradiated in foil specimens of type 304 stainless steel. An irradiation effect in the surface region of the foil specimens has been investigated by means of glancing angle X-ray diffraction (GXRD), Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) in order to observe the retained rare-gas atoms and elucidate their correlation with the ion-induced martensitic phase transformation of γ phase → α phase. It has been seen that the amounts of Ar, Kr and Xe retained in stainless steel as estimated from PIXE spectra were affected by the sputtering under ion irradiation. It has been shown by GXRD measurements that the retained rare-gas atoms agglomerated and formed a highly-pressurized solid phase inclusion. It is clear from GXRD measurements that the amount of the phase transformation at saturation increased linearly with increasing ion range of the implanted rare-gas atoms irrespective of the ion species. We speculate from this linearity that the depth distribution of the ion-induced martensitic phase may overlap with that of the rare-gas inclusion in stainless steel, and the formation of the rare-gas inclusion has stress-induced the phase transformation of γ → α. However, before saturation of the ion-induced phase transformation, the degree of the phase transformation in stainless steel as estimated from the amount of retained rare-gas atoms clearly differed for the different ion species.