THERMAL NUCLEATION AND GROWTH OF He BUBBLES IN He IMPLANTED STAINLESS STEELS

Nucleation and growth of He bubbles at different annealing temperatures T≤1023 K in stain-less steels HR-2 and SS321,implanted with He~+(40-70 keV.1×10~(16)-6×10~(17) He~+/cm~2),were ohserved under TEM.T=0.45T_m seems to be a transitiontemperature.The He bubbles continue mainly their nucleation at 0.3T_m< T<0.45T_m,andgrow predominantly at T≥0.45T_m,due probably to migration and coalescence by surfacediffusion of metal atoms around the bubbles.The apparent activation energies for the growthare found to he 0.41 and 0.31 eV for HR-2 and SS321 respectively.The bubble density inHR-2 is greater than that in SS321 within whole measuring temperature range,and the onsettemperature of rapid swelling is also higher.It is believed that the resistance of HR-2 to He issuperior to that fo SS321.