Residual stress relaxation in shot peened Timetal 21s

Selective surface aging treatments (mechanical surface treatment followed b y aging) on beta-titanium alloys can result in higher endurance limits than conventional mechanical surface treatments. An explanation of fatigue beha viour of selectively surface aged parts should not only consider preferenti al precipitation strengthening but also take into account the remaining res idual stresses. The beta-titanium alloy Timetal 21s with two oxygen content s (0.15 and 0.30 wt%), in two solution treated conditions (fully and partia lly recrystallized) was aged at temperatures between 350 and 500 degrees C after shot peening. Microhardness and X-Ray measurements allowed the determ ination of the degree of precipitation strengthening and relaxation of resi dual stresses, respectively, in the near surface regions during aging. (C) 1999 Elsevier Science S.A. All rights reserved.