Abstract
The triggering mechanism of secondary recrystallization was investigated using oxide dispersion strengthened superalloys MA6000 and MA754. Secondary recrystallization occurs abruptly at 1498 K in MA6000, and in the range 1403–1453 K in MA754. In MA6000, preannealing below 1382 K causes secondary recrystallization during subsequent annealing at 1553 K, whereas preannealing in the temperature range 1382–1498 K causes no secondary recrystallization during subsequent annealing at 1553 K. However, in MA754, secondary recrystallization is accomplished independently of the preannealing temperature. There is a critical heating rate for the occurrence of secondary recrystallization in MA6000, while in MA754 secondary recrystallization occurs independently of the heating rate in the range tested 0.5–16 K min −1. In MA6000 round Ni-(20–40)at.%Al-(10–20)at.%Cr oxide particles grow during secondary recrystallization up to about 130 nm in diameter which is four times larger than that of the as-extruded sample, whereas significant coarsening of yttrium oxide particles is not detected. The coarsening of Ni-(20–40)at.%Al-(10–20)at.%Cr oxide particles triggers secondary recrystallization in MA6000. In MA754, yttrium oxide particles are involved in secondary recrystallization and the occurrence of secondary recrystallization over a wide temperature range is attributed to the inhomogeneous distribution of yttrium oxide particles.
Published Version
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