Strengthening at high temperatures by precipitates in Fe–Al–Nb alloys

The addition of Nb to Fe3Al-base alloys has been shown to improve strength for temperatures below about 700 °C, but thereafter the strength gains are minimal. Changes of order and precipitation occur on annealing of quenched Fe–Al–Nb alloys at temperatures in the range of about 600–800 °C, and these are responsible for the changes of mechanical properties. Factors responsible for the poor precipitate stability and loss of strength are examined, which include the role of interface structure on destabilizing precipitates of the intermediate phase which forms, promoting its transition to the stable Laves phase, as well as allowing rapid coarsening of Laves precipitates.