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The Microstructures and Stresses group studies the genesis of microstructures by phase transformations in the solid state and internal stresses during thermal, thermomechanical or thermochemical treatments of metallic alloys. Indeed, the relationships between the different elements of the treatment / microstructures / properties chain need to be known to design and to improve these metallic alloys.

The group's activities are aimed at:

  • understanding the mechanisms of microstructures formation by phase transformations in the solid state
  • establishing the relationships between microstructures and the generation of stresses during phase transformations
  • establishing the relationships between microstructures, stresses and properties ( particularly mechanical properties)

The metallic alloys studied are multi-constituent alloys, but we also examine model alloys (pure, binary, ternary metals). The applications targeted concern the lightening of structures (for the aeronautics and automotive industries) via the optimisation of microstructures generated by different processes (forging, stamping, heat treatments, etc.) or recycling.

A specificity of the group is the study of phase transformation kinetics in situ (dilatometry, resistivimetry, Xray Diffraction by synchrotron radiation, microscopy) under thermal/thermomechanical treatments (temperatures up to 1200°C, speeds varying from 0.01°C/s to 200°C/s). Interactions between stresses and phase transformations are studied: internal stresses are associated with transformation deformation tensor – and/or applied external stresses.

The experimental activities are based on joint modelling work at different scales and combining various approaches (Calphad, phase field, mean fields). Most often, microstructural evolution models are associated with micromechanical models, using different techniques such as finite elements to take into account the local mechanical behaviour at the phase scale.

The group also carries out modelling and numerical simulations during heat treatment at the scale of massive parts (residual stresses, deformations), in the presence of thermal and chemical gradients and taking into account thermal - phase transformation - mechanical couplings.

All of this research is carried out with :

  • Academic partners: LEM3, CEMES, Institut P’, Mines ParisTech, SIMAP, GPM, ICMCB, ONERA
  • Industrial partners: SAFRAN, Arcelor Mittal, Ascometal CREAS, AIRBUS, Vallourec, PSA, Bosch, IRT M2P, etc.

The group is also strongly implicated in the Labex DAMAS (Design of Alloy Metals for low-mAss Structures).

The group is involved in a number of European H2020 projects under the RFCS (Research Fund for Coal and Steel) programme, including:

  • IMMAC: Machinability of high-strength steels, terminé à enlever?
  • STEELSECO (Design of new economic secondary precipitating steels for fatigue resistance at elevated service temperatures)
  • MIPRE (Advanced metallurgical and micromechanical modelling to deploy the microstructural tailoring potential of press hardening)
  • DYNAUSTAB (Austenite Stability under Dynamic loading).

The group also participates in ANR projects:

  • HighS Ti: obtaining high-strength harmonic microstructures in titanium alloys by powder metallurgy
  • ALTITUDE (new high temperature titanium alloy for tomorrow's aeronautic applications)
  • ECUME (Interactions between electric currents and microstructural evolutions)


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