Metallurgical Transactions

, Volume 4, Issue 1, pp 47–59 | Cite as

Morphology of y’ and y” precipitates and thermal stability of inconel 718 type alloys

  • R. Cozar
  • A. Pineau


The precipitation of the γ (Ll2) and γ" (DO22) phases has been studied in four alloys Fe-Ni-Cr-Ti-Al-Nb containing a higher Ti + Al/Nb ratio than that of the INCONEL 718 alloy. For these alloys, the precipitation microstructure varies rapidly with aging temperature and composition. Bct γ"particles have always been found to precipitate on γ phase. Moreover, by aging three alloys above a critical temperature, a “compact ntorphology” has been observed: cube-shaped γ particles coated on their six faces with a shell of γ" precipitate. This microstructure has proved to be very stable on prolonged aging. A thermal stability better than that encountered in nominal INCONEL 718 alloy can thus be achieved. The influence of composition and aging temperature on the conditions that bring about this “compact morphology” has been investigated. A minimal Ti + Al/Nb ratio between 0.9 and 1 has been determined, allowing the “compact morphology” to be obtained.


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Copyright information

© American Society for Metals, The Melallurgical Society of AIME 1973

Authors and Affiliations

  • R. Cozar
    • 1
  • A. Pineau
    • 1
  1. 1.Centre des Matériaux deL’Ecole des Mines de ParisCorbeil-EssonnesFrance

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