Sous la direction de : Jean-Jacques Blandin

Comportement mécanique des verres métalliques massifs - Effet d’une cristallisation partielle

• Sous la direction de :

• Jean-Jacques Blandin

Mechanical behavior of bulk metallic glasses - Impact of the partial crystallization

• Supervised by :

• Jean-Jacques Blandin

Conventional solidification

• Cooling a metal

•  Crystallization

Production of a metallic glass

• Cooling a metal

•  Crystallization

Aim of the work

Room temperature

Room temperature

• E ≈ corresponding crystalline alloys

• +

• f = 1830 MPa ( 1 %)

•  elast ≈ 0.02

Room temperature

• Loading curve :
• L = C h2
• Unloading curve:

• ( Irreversible Work ratio )

• RW = Wirr / Wtot

Room temperature

• Loading curve :
• L = C h2
• Unloading curve:

• ( Irreversible Work ratio )

• RW = Wirr / Wtot

Room temperature

• Loading curve :
• L = C h2
• Unloading curve:

• ( Irreversible Work ratio )

• RW = Wirr / Wtot

Room temperature

Room temperature

Room temperature

High temperature

High temperature

• Confirmation of usual deformation behaviour in SLR

• Newtonian regime
• High temperature / low strain rate
• Non Newtonian regime
• Low temperature / high strain rate

High temperature

• effect of T : just translation

High temperature

• effect of T : just translation

High temperature

High temperature

Crystallization / Microstructure

• Various heat treatments

Crystallization / Microstructure

• Various heat treatments

Crystallization / volume fraction

Crystallization / volume fraction

• To calculate the real volume

• fraction we need to have only

• one crystal type :

• Crystallite size
• Crystallite nature

Crystallization / volume fraction

• Crystals randomly oriented
• Density constant
• (d / d < 1 %)

Crystallization / volume fraction

• Crystals randomly oriented
• Density constant
• (d / d < 1 %)

Crystallization / volume fraction

• Equivalent values with the two methods :

•  Validation of the measurement methods

• XRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)

Crystallization / volume fraction

• Equivalent values with the two methods :

•  Validation of the measurement methods

• XRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)

Crystallization / volume fraction

• Equivalent values with the two methods :

•  Validation of the measurement methods

• XRD analysis is an accurate way to measure Volume fraction of crystals (even for small crystallites)

Effect of crystallization / room temperature

• Fracture stress increases slightly and then falls !

Effect of crystallization / room temperature

Effect of crystallization / room temperature

• Effect of crystallization

• (Fv < 0.5)

• Very limited variations of Rw and C/Eeq
• Still sensitive to pressure

Effect of crystallization / high temperature

• Two main effects of crystallization

• Increase of viscosity
• Promotion of non Newtonian behaviour

Effect of crystallization / high temperature

Effect of crystallization / high temperature

Effect of crystallization / high temperature / reinforcement

• Prediction of R from mechanical models ?

• Hard sphere dispersion in a viscous media : Krieger model

Effect of crystallization / high temperature / reinforcement

• Prediction of R from mechanical models ?

• Hard sphere dispersion in a viscous media : Krieger model

Effect of crystallization / high temperature / reinforcement

• Prediction of R from mechanical models ?

• Hard sphere dispersion in a viscous media : Krieger model

Effect of crystallization / high temperature / reinforcement

Effect of crystallization / high temperature / reinforcement

Effect of crystallization / high temperature / activation energies

Effect of crystallization / high temperature / activation energies

Effect of crystallization / high temperature / activation energies

Effect of crystallization / high temperature / activation energies

Perspectives / scientific

Perspectives / scientific

Perspectives / scientific

Perspectives / technological

Merci à … Ludovic Charleux Béatrice Doisneau-Cottignies Patricia Donnadieu Marc Fivel Alexandre Mussi Jean-Marc Pelletier Luc Salvo Jean-Louis Soubeyroux Michel Suery André Sulpice Marc Verdier Qing Wang … pour leurs contributions à ce travail

Conclusion and ….perspectives

• Crystallites size effect (heat treatments at other temperatures)
• Room temperature
• Young modulus
• High temperature
• Model of deformation based on the Argon model
• Effect of the high temperature deformation on the crystallization

Perspectives / scientific

Poisson ratio … deformation mechanism

Crystallisation

• Three crystallization events may occur at higher temperature…

• Analyze here the two first crystallization peaks

DMA / Activation energy

• Activation energy:

• T

Effect of crystallization : Newtonian Viscosity

Effect of the deformation on the crystallization

Effect of the deformation on the crystallization

Effect of the deformation on the crystallization

High temperature Mechanism

High temperature Mechanism

High temperature Mechanism

Co-extruded materials

Co-extruded materials

Co-extruded materials

Co-extruded materials

Co-extruded materials