No abstract

An intermediate heat treatment at 1550°F used to improve the rupture ductility of INCONELY: alloy 706 had a varied effect on room-temperature yield strength of the alloy. The effect seemed to depend on very small differences in aluminum content. A laboratory investigation was conducted to determine the effects of variations in aluminum content and heat treatment on the yield strength of alloy 706. Samples having aluminum contents from 0.033% to 0.90% were studied after being subjected to four different heat treatments. The investigation produced an explanation of the variations in yield strength in terms of changes in structure of gamma prime, gamma prime/ lattice mismatch, and changes in modulus of elasticity. It was found that material age-hardened without the intermediate treatment is in a slightly underaged condition, and that yield strength of such material is a function of gamma prime particle properties. It was also found that material given the 1550°F intermediate treatment and then age-hardened is slightly overaged. The yield strength of overaged material is not a function of gamma prime properties but depends instead on matrix shear modulus and interparticle spacing of the gamma prime.

Companion laboratory-scale studies were conducted on specimens of ESR alloy 718 in order