Stability of Several Oxide Dispersion Strengthened Alloys and a directionally solidified y/y′ ‐α eutectic alloy in a thermal gradient

Thermal gradient testing of three oxide dispersion strengthened alloys (two Ni‐base alloys, MA 754 and MA 6000E, and the Fe‐base MA 956) and the directionally solidified eutectic alloy, γ/γ′‐α, have been conducted. Experiments were carried out with maximum temperatures up to 1200°C and thermal gradients on the order of 100°C/mm. The oxide dispersion strengthened alloys were difficult to test because the thermal stresses promoted crack nucleation and growth; thus the ability of these alloys to maintain a thermal gradient may be limited. The stability of individual fibers in γ/γ′‐α was found to be excellent; however, microstructural changes were observed in the vicinity of grain boundaries. Similar structures were also observed in isothermally annealed material; therefore thermal gradients do not affect the microstructure of γ/γ′‐α in any significant manner.