Behavior of ion-implanted helium and structural changes in nickel-base alloys under long-time exposure at elevated temperatures

The regularities of helium trapping and release and structural changes in t he model alloys of a Ni-Al system after post-irradiation annealings at 920- 1120 K up to 25 h have been studied by means of thermodesorption spectromet ry (TDS), internal friction (IF) measurement and transmission electron micr oscopy (TEM). The samples were irradiated by He+-ions at room temperature u p to fluence of 5 x 10(20) m(-2). It was shown that the quantity of helium remaining in Ni is considerably less than in solid solutions after long-tim e post-irradiation annealing at 1020 and 1070 K. The IF measurements showed that irradiation resulted in the formation of additional peaks in the IF s pectra which were not detected in the IF spectra of unirradiated samples. T he obtained data give grounds to propose that more thermally stable complex es containing vacancies, helium and alloying element atoms (complexes of He mAlkVn type) can be formed in the substitutional solid solutions along with usual complexes of HemVn type in pure nickel. (C) 1999 Elsevier Science B. V. All rights reserved.