Author(s)

M.-C. Berger & J.K. Gregory

Abstract

Through aging after a conventional mechanical surface treatment (Selective Surface Aging: SSA), the fatigue behavior of precipitation hardenable alloys can be further improved over the mechanically surface treated condition. Compressive residual stresses remaining in the age hardened surface layers may cause this attractive behavior. To better understand and control the SSA treatment, the precipitation hardening and the relaxation of residual stresses during aging were examined in surface layers of the shot peened metastable (3-Ti alloy Timetal 21s. Aging treatments were carried out at temperatures between 350 and 500°C, for two oxygen levels and two initial degrees of cold work. Although precipitation reactions occur early in the strongly cold worked s

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