Effect of weld thermal cycle and restraint stress on helium bubble formation in stainless steels

Helium bubble structure was examined in helium-implanted stainless steels a fter applying thermal cycles and tensile stresses using a weld thermal and stress cycle simulator. SUS304 specimens implanted with helium ions to 5 ap pm were heated at 1473 K for 2 s in an argon gas atmosphere. The heat-up ra te and cooling rate were controlled to be 90 and 130 K/s, respectively. Ten sile stresses ranging from 0 to 4 MPa were applied immediately after reachi ng a temperature of 1473 K. TEM observation revealed that bubble formation occurred even after short annealing times and that the size of the helium b ubbles was strongly dependent on the tensile stress during heating. (C) 200 0 Elsevier Science B.V. All rights reserved.