Structural heredity in the U-6Nb alloy and conditions for its elimination

The conditions have been determined for the manifestation of structural heredity in the U-6 wt % Nb alloy with the restoration of the size and shape of grains of the initial high-temperature γ phase in the course of the forward γ → α″ martensitic transformation upon cooling and the reverse α″ → γ transformation upon heating. Contrary to iron-based alloys, the restored γ phase does not undergo recrystallization due to phase-transformation-induced deformation (phase naklep) upon subsequent high-temperature heating. The elimination of structural heredity with a noticeable grain refinement (by almost an order of magnitude, down to 10–20 μm) in the high-temperature γ phase occurs in the process of the repeated quenching from 700°C after the use of one of the preliminary heat treatments (cold deformation of the α″ martensite, the recrystallization of the deformed α″ phase, the high-temperature aging of the initial α″ martensite, and eutectoid decomposition).

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