HYDROGEN TRAPPING IN AGED BETA-TITANIUM ALLOYS

Hydrogen trapping in three beta-titanium alloys (unaged and aged Ti-15 V-3Cr-3Al-3Sn and Beta-21S, and partially aged Beta-C) was investigate d using a potentiostatic pulse technique. The apparent trapping consta nt (k(a)) and hydrogen entry flux were determined for each alloy in 1 mol l(-1) acetic acid/l mol l(-1) sodium acetate. The results were com pared with those for other beta-Ti alloys (Ti-10V-2Fe-3Al, Ti-13V-11Cr -3Al and fully aged Beta-C) studied previously. Aging caused a negligi ble change in k(a) for Ti-15-31 whereas a marked increase was observed for Beta-21S and the other beta-Ti alloys. Among the aged alloys, Ti- 13-11-3 had the highest value of k(a) and Ti-15-3 had the lowest value . The intrinsic susceptibilities of Beta-C and Beta-21S to hydrogen em brittlement (HE), as represented by the trapping constants, were compa rable and significantly higher than that of Ti-15-3. The susceptibilit ies were consistent with the relative resistances to HE observed for t hese alloys. (C) 1997 Acta Metallurgica Inc.