Metallurgical and Materials Transactions A

, Volume 45, Issue 7, pp 2963–2982 | Cite as

Microstructural Evolutions During Thermal Aging of Alloy 625: Impact of Temperature and Forming Process

  • Lorena Mataveli Suave
  • Jonathan Cormier
  • Patrick Villechaise
  • Aurélie Soula
  • Zéline Hervier
  • Denis Bertheau
  • Johanne Laigo
Article

Abstract

The microstructural evolutions occurring upon thermal aging of alloy 625 sheets were studied in the 823 K to 1173 K (550 °C to 900 °C) temperature range and for durations up to 2000 hours. TTT diagrams of the δ and γ″ phases were established based on high-resolution scanning electron microscopy and associated quantitative image analysis approaches. The evolutions of secondary carbide volume fraction were also characterized. It was observed that the precipitation domains of the γ″ and δ phases are, respectively, 823 K to 1023 K (550 °C to 750 °C) and 923 K to 1173 K (650 °C to 900 °C) and that the γ″ coarsening follows the LSW theory once these particles have an ellipsoidal morphology. The onset of grain growth, accompanied with an increase of the texture index, was observed at a temperature as low as 1173 K (900 °C). It results from the progressive dissolution of grain boundaries’ secondary carbides (especially M6C carbides) at this temperature, a process that favors a greater mobility of grain boundaries. It is also shown that the forming process (shear spinning), even after a relaxation heat treatment, enhances and stabilizes the precipitation of the δ phase compared to as-rolled + solution heat-treated sheets. It hence slows down the precipitation of the γ″ phase, a result that is in good agreement with a thermal aging that was performed under load (i.e., during a creep test).

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 2014

Authors and Affiliations

  • Lorena Mataveli Suave
    • 1
    • 2
  • Jonathan Cormier
    • 1
  • Patrick Villechaise
    • 1
  • Aurélie Soula
    • 1
    • 5
  • Zéline Hervier
    • 3
  • Denis Bertheau
    • 1
  • Johanne Laigo
    • 4
  1. 1.Physics and Mechanics of Materials DepartmentInstitut Pprime, UPR CNRS no. 3346, CNRS – Université de Poitiers – ISAE-ENSMAFuturoscope, ChasseneuilFrance
  2. 2.Materials and Process DepartmentAircelle – SAFRAN GroupGonfreville-L’OrcherFrance
  3. 3.Materials, Processes and Investigations DepartmentTurbomeca – SAFRAN GroupBordes CedexFrance
  4. 4.Materials and Process DepartmentSnecma – SAFRAN GroupMoissy-CramayelFrance
  5. 5.Plaisir CedexFrance

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