Nano‐scale phase transformation in Ti‐implanted austenitic 301 stainless steel

Phase‐transformation behaviours were investigated for austenitic 301 stainless steel during implantation at room temperature with 300 keV Ti ions to fluences of 8 × 1019∼3 × 1021 ions m−2 by means of transmission electron microscopy. The cross‐sectional specimen was prepared using a focused ion beam. Plan observation of the implanted specimen showed that phase transformation from γ‐phase to α‐phase was induced by implantation to a fluence of 3 × 1020 Ti ions m−2. The nucleation of the irradiation (implantation)‐induced phase increased with the increase of the dose. The orientation relationship between the γ matrix and the induced α martensitic phase was identified as (011)α//(111)γ and [11‐1]α//[10‐1], close to the Kurdjumov–Sachs relationship. Cross‐sectional observation after implantation to a fluence of 5 × 1020 ions m−2 showed that phase transformation mostly nucleated near the surface and occurred in the higher the concentration gradient of the implanted ion, i.e. a higher stress concentration takes place and this stress introduced by the implanted ions acts as a driving force for the transformation.