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For the oxide dispersion strengthened CODS) alloys, dislocation-particle interaction is generally believed to be repulsive since the elastic constants of the oxide dispersoids are believed to be greater than those of the matrix. High temperature strengthening is thought of in terms of a dislocation climb modified Orowan type bowing mechanism between the particles. Dislocation escape occurs when the stress is sufficient to cause the dislocation to bow to a critical configuration. Contrary to this general belief, through detailed THM microscopy study of crept and hot tensile tested Inconel MA 754, we have found and will report in this paper that the interaction between dislocation and oxide dispersoid is in fact attractive, with the high temperature properties of ODS alloys stemming from this unexpected attractive interaction. In particular, the characteristic and important threshold behavior of ODS alloys during creep at high temperatures is discussed. It is proposed that the finding of attractive interaction opens new avenues for the alloy design of ODS alloys, including the pinning of dislocations next to the dispersoids by additional elements and tlhe purposeful introduction of non-adherent interfaces between dispersoids and matrix. In the limit, the high temperature (or low strain rate) threshold stress of, say, Inconel MA 754 at 1093 deg. C, can be increased by a factor of two from 94 MPa (14 ksi) to 188 MPa (28 ksi).

Attractive Dislocation and Particle Interactions in ODS Superalloys - and Implications