ABSTRACT
Early attempts to produce oxide dispersion-strengthened (ODS) nickelbased alloys by chemical means were restricted in that the contents of reactive elements such as AI or Ti had to be kept to a minimum. In the case of internal oxidation of dilute metallic solid solutions to manufacture ODS alloys, AI and Ti will oxidize during the dispersoid formation sequence. For methods involving the selective reduction of mixed oxides, Al20 3 and Ti02 cannot be reduced in the matrix formation step. Coprecipitation of fine dispersoid and matrix powders was an important breakthrough in achieving the correct geometric conditions of both fine dispersoid and interparticle spacing for dispersion strengthening and facilitated the Du Pont introduction of TD nickel and TD nichrome• (Alexander, 1961, 1965). However, production expense and the limitation to simple, singleelement or solid-solution matrices restricted the alloy content of such materials. In other work the addition of insoluble refractory oxides by injection into an alloy melt reported by Williams et al. (1960) was found to be unsatisfactory because of oxide agglomeration and resulting inhomogeneous dispersoid distributions.
