IRON-BASE, OXIDE DISPERSION-STRENGTHENED ALLOYS - TENSILE, CREEP AND LOW-CYCLE FATIGUE BEHAVIOR

Oxide dispersion strengthened (ODS) alloys have been developed for hig h creep strength at high temperatures. The iron-base variety, containi ng about 5 wt% aluminium, additionally exhibits excellent corrosion re sistance at temperatures up to 1523K. These alloys are therefore promi sing materials for high temperature components in aggressive environme nts. The dispersoids are small yttria particles which ate significantl y more stable than carbide or gamma'-precipitates in conventional high temperature alloys. They slow down dislocation glide by a newly detec ted interaction mechanism. Its formulation allows the stress dependenc e of the creep rate of these materials to be modelled. Low cycle fatig ue(LCF) properties are highly dependent on thermo-mechanical pretreatm ent by which different grain structures are produced. Nevertheless, LC F testing revealed a flow strain nearly independent of grain size, and reveals Young's modulus as a basic parameter for cyclic life. In this paper, the main properties of iron-bass ODS-alloys will be outlined a nd it will be shown how far the correlation between the underlying mec hanisms and the technologically relevant behaviour is presently unders tood.