Critical cavity sizes in dual-ion bombarded 304 SS. Pt. 2

The rate theory of irradiated metals, as developed by Bullough and Brailsford, is used to characterize the microstructure of a material in which gas-filled cavities exist. The growth dynamics of one such cavity is then carefully analyzed. The critical radius concept discussed by Hayns and Russell has been refined in terms of the 'blocking point' of Lifschitz and Slyozov; this permits a detailed tracing of the transition from equilibrium bubble growth to the displacement-limited case. Use of Van der Waals equation of state for helium gas in the cavity has a surprisingly large effect on the dynamics of smaller cavities. Comparison is made between the theoretical blocking point radius and the experimental values of critical radius in stainless steel based on the helium inventory method. Good agreement is found below 6500C, but high temperatures lead to serious disagreements. (orig.)