Nickel-base single crystal superalloys with Ru additions of 5.7 to 9.7 wt%, moderate amounts of refractory elements and up to 6.7 wt% Cr were investigated. The ' precipitate morphology of the experimental alloys was cuboidal, near-spherical and intermediately-shaped depending on the Cr and Ru content. The time to 1% creep and the creep rupture lives of the experimental alloys were measured at 950°C and 290 MPa. Within the set of alloys investigated rafting occurred parallel to the axis of the applied uniaxial tensile stress, perpendicular to the applied stress or was completely suppressed, suggesting a wide range of lattice misfit. Interfacial dislocation network development during creep also varied widely among the alloys investigated. The possibilities for control of microstructure and high temperature properties via Ru additions are discussed.

Phases present in a series of model ruthenium containing Ni-base single crystal superalloys were investigated in both as-solidified and heat-treated crystals. Three unusual Ru-rich phases have been identified including a L2 1 Heusler phase with a composition of Ru 2 AlTa, a B2 RuAl phase and a hcp Re(Ru)-rich phase. These phases have been characterized in terms of the microstructure, composition, crystallography, three-dimensional morphology and distribution within the dendritic microstructure via X-ray, SEM and TEM analyses.

Three unusual Ru-rich phases have been identified in a multicomponent Ni-base single crystal superalloy, including a L21 Ru2AlTa Heusler phase, a B2 RuAl phase and a hcp Re(Ru)-rich δ phase. These phases have their own preferential precipitation location within the dendritic structure. No conventional topologically-close-packed (TCP) phases have been observed with thermal exposure at 950oC for 1500 hours.

The shell of the Space Shuttle's External Tank is 2219-T87 aluminum to which an epoxy primer is applied to allow bonding of the Thermal Protection System (TPS). A chromate deoxidizer is used to prepare the aluminum surface for primer bonding. In this study, scanning electron microscopy (SEM) was used to characterize the surface morphology of 2219-T87 aluminum associated with different bond strengths produced by varying the deoxidizer treatment parameters.Eight sets of two 2219-T87 aluminum panels were treated with chromate deoxidizer. One set was used as a control. The second set was subjected to an additional deoxidizer treatment, while the third set received two additional deoxidizer treatments. The fourth, fifth, and sixth sets were held for 5, 10, and 15 minute post deoxidiation and prior to final rinse with demineralized water. The two remaining sets were deliberately contaminated with 25:1 and 100:1 water:deoxidizer solutions, which were allowed to dry on their surfaces.