Precipitation behavior of oxide dispersion strengthened Alloy 617

Oxide dispersion strengthened Alloy 617 was prepared by mechanical alloying and hot extrusion processes. Precipitation behavior during heat treatment was evaluated by XRD, SEM and TEM. It was revealed that the dominant precipitates in the solution-annealed sample were Cr-rich M₂₃C₆ and M₆C precipitates on grain boundaries, and Al–O, Y–Al–O and Y–Ti–O nano-particles in grain interior. Different from a conventional Alloy 617, TiN and TiC precipitates were not found. Aging at 760 °C for 100 h showed that γ′ were not formed, possibly due to the high affinity of O to Al and Ti, which suppressed the formation TiN, TiC and γ′. Heat treatment at high temperatures showed that M₂₃C₆ and Y₂Ti₂O₇ were stable up to 1300 °C, while most Al–O nano-particles evolved into Y–Al–O. The high thermal stability of fine Y₂Ti₂O₇ particles with a high number density is expected to contribute to a superior high temperature mechanical strength than γ′ precipitates .