Effect of co-addition of phosphorus and titanium on point defect behavior and precipitation in austenitic stainless steel under electron irradiation

Microstructural evolution and radiation induced segregation under electron irradiation have been observed with a HVEM in pure Fe-16Cr-17Ni-0.1P-(0.1 approximately 0.25) Ti alloys. It was shown that P atoms served as the nuclei for interstitial loops in the alloy containing both P and Ti as well as the alloy containing P only. In the alloys containing both P and Ti, vacancy loop formation was prominent even at higher temperatures compared with alloys containing P only. These phenomena resulted in a remarkable suppression of void swelling and radiation-induced Ni depletion in matrices. The swelling suppression seemed to be related with the P concentration in matrices. Because of the strong interaction between P and Ti, P segregation to the defect sinks (grain boundary, dislocation and free surface) was retarded maintaining the P effect to suppress swelling in the matrix. The formation of M₂P-type phosphides which act as defect sinks at higher temperatures was enhanced by Ti addition. These results suggest that the co-addition of P and Ti is very effective for increasing swelling resistance.