The Effects of Small Deformation on Creep and Stress Rupture of ODS Superalloys.

摘要

This research program aims to enhance understanding of the effects of predeformation on the creep and stress rupture of oxide dispersion strengthened (ODS) alloys and also of the cyclic creep and cyclic stress rupture behavior of ODS alloys. During the third program year, the research effort was focused on the 760 C cyclic creep behavior of MA 6000E, an advanced ODS superalloy that is strengthened by a unique combination of upsilo prime precipitates and oxide dispersoids for both intermediate and elevated temperature strength. Cycling the load at 760 C resulted in a dramatic decrease in the minimum strain rate and an increase in the rupture life relative to the static case (no load cycling). The magnitude of the effect increased as the cyclic period decreased--there is an order of magnitude decreased in the minimum creep rate in going from a static test to a cyclic period of ten minutes. The creep deceleration involves storage and recovery of anelastic strain, and this mechanism is discussed and modeled. Comparisons of the cyclic creep properties of ODS alloys and conventional superalloys show that the effects of reduced minimum creep rate and extended rupture life due to cyclic loading during creep are more significant and pronounced in ODS alloys than in other alloys and superalloys that are not dispersion strengthened.