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

Comportement mécanique des verres métalliques massifs - Effet d’une cristallisation partielle. Sébastien Gravier. Sous la direction de : Jean-Jacques Blandin. Mechanical behavior of bulk metallic glasses - Impact of the partial crystallization. Sébastien Gravier. Supervised by :

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

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  1. Comportement mécanique des verres métalliques massifs-Effet d’une cristallisation partielle Sébastien Gravier Sous la direction de : Jean-Jacques Blandin

  2. Mechanical behavior of bulk metallic glasses-Impact of the partial crystallization Sébastien Gravier Supervised by : Jean-Jacques Blandin

  3. Conventional solidification • Cooling a metal •  Crystallization Volume Tm Temperature Solid state Liquid state

  4. Production of a metallic glass Metallic glass Tg Glassy state • Cooling a metal •  Crystallization To avoid crystallization  Rapid cooling Volume Limited size ! Tm Temperature More complex compositions to have Bulk metallic glasses Supercooled Liquid Region (SLR) Liquid state

  5. Aim of the work Tg Nanocrystals Room temperature : RT (T << Tg) High temperature : HT (T>Tg) 100 nm brittleness large strain 5 mm Glassy state Supercooled Liquid Region Tg Crystallization Volume Temperature Effects ?

  6. Mechanical characterisation methods Validation for the amorphous alloy Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression nanoindentation DMA How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  7. DSC XRD TEM Microstructural characterisation Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy Crystal volume fraction ? How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  8. Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy DSC XRD TEM Microstructural characterisation Crystal volume fraction ? How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  9. Room temperature Elements Zr Ti Cu Ni Be Atomic % 41.2 13.8 12.5 10 22.5 BMG studied in this thesis Vit1 (Tg = 365 °C )

  10. Room temperature E Microscopic plasticity Fracture surface elast Elements Zr Ti Cu Ni Be Atomic % 41.2 13.8 12.5 10 22.5 BMG studied in this thesis Vit1 (Tg = 365 °C ) • E ≈ corresponding crystalline alloys • + • sf = 1830 MPa ( 1 %) • eelast≈ 0.02 Macroscopic brittleness  f  Compression tests at room temperature on a BMG Macroscopic brittleness but local plasticity

  11. Room temperature L h • Loading curve : • L = C h2 • Unloading curve: • ( Irreversible Work ratio ) • RW = Wirr / Wtot Nanoindentation loading and unloading curves Collaboration: L. Charleux ( INP-Grenoble )

  12. Room temperature Wirr Wtot • Loading curve : • L = C h2 • Unloading curve: • ( Irreversible Work ratio ) • RW = Wirr / Wtot = 67 % > Silica Glass ≈ 40 % < Aluminium ≈100 % Suggest many dissipative events ! Nanoindentation loading and unloading curves

  13. Room temperature Wirr Wtot • Loading curve : • L = C h2 • Unloading curve: • ( Irreversible Work ratio ) • RW = Wirr / Wtot Sd = 67 % > Silica Glass ≈ 40 % < Aluminium ≈100 % Suggest many dissipative events ! • AFM measurements : • reduced Young modulus : Eeq Nanoindentation loading and unloading curves Materials Science and Engineering A (2006)

  14. Room temperature In this plane • Von Mises criterion : sy  Line in this plane Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior

  15. Room temperature  > 0  < 0 In this plane • Von Mises criterion : sy  Line in this plane • Drucker Pragger criterion : sy and α (pressure sensitivity) • Upper part :  > 0 • Lower part :  < 0 Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior

  16. Room temperature  > 0  < 0 In this plane • Von Mises criterion : sy  Line in this plane • Drucker Pragger criterion : sy and α (pressure sensitivity) • Upper part :  > 0 • Lower part :  < 0  Both values of sy in agreement with compression in agreement with Vaidyanathan 2001 Patnaik 2004 Plasticity map extracted from nanoindentation curves: gives plastic properties independently of elastic behavior Nanoindentation: Fruitful technique to study deformation at room temperature (in particular pressure sensitivity)

  17. Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy DSC XRD TEM Microstructural characterisation Crystal volume fraction ? How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  18. High temperature Compression tests at Tg + 10 °C, various strain rates Large strains Viscoplastic deformation in steady state Viscosity as function of strain rate / compression

  19. High temperature • Confirmation of usual deformation behaviour in SLR • Newtonian regime • High temperature / low strain rate • Non Newtonian regime • Low temperature / high strain rate Non Newtonian Newtonian Viscosity as function of strain rate / compression

  20. High temperature Complex multiatomic mechanism (activation volume ≈ 20 atoms) in large strain … Suppose: Q = 440 kJ/mol (strong temperature sensitivity) Ability to draw a master curve: • Sensibility of viscosity to strain rate independent of temperature • effect of T : just translation Sensitivity to temperature: • Newtonian viscosity Creation of a unique master curve for various temperatures

  21. High temperature Complex multiatomic mechanism (activation volume ≈ 20 atoms) in large strain … Suppose: Q = 440 kJ/mol Ability to draw a master curve: • Sensibility of viscosity to strain rate independent of temperature • effect of T : just translation Sensitivity to temperature: • Newtonian viscosity Creation of a unique master curve for various temperatures Data obtained in steady state (large strain) Is there a minimum strain to measure these features ?

  22. High temperature T Frequency scans at various fixed temperatures Dynamic Mechanical Analysis (DMA) : Sinusoidal small strain tests Phase difference between applied stress and strain Dissipative part of the deformation : Construction of a master curve Collaboration: Jean–Marc Pelletier, INSA - Lyon

  23. High temperature Dynamic Mechanical Analysis (DMA) : Sinusoidal small strain tests Phase difference between applied stress and strain Dissipative part of the deformation : T Elementary mechanism of deformation independent of T Apparent activation energy ~ 400-450 kJ/mol  Similar mechanical behaviours in the investigated conditions (T and both small and large strains) DMA + Compression : Fruitful techniques to study deformation at HT in a large strain interval Frequency scans at various fixed temperatures Construction of a master curve Collaboration: Jean–Marc Pelletier GEMPPM, INSA

  24. DSC XRD TEM Microstructural characterisation Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy Crystal volume fraction ? How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  25. Crystallization / Microstructure Amorphous : transformed fraction Ft = 0% Crystallite average size Φ ~ 35 nm Ft ≈ 100 % ~ 30 nm Ft = 10 % Φ ~ 35 nm Ft = 80 % Φ~ 35 nm Ft = 60 % Φ ~ 30 nm Ft = 45 % 60 min. 45 min. 10 min. 30 min. 20 min. Isothermal annealing DSC at Tg + 50 °C • Various heat treatments

  26. Crystallization / Microstructure Amorphous : transformed fraction Ft = 0% Crystallite average size Φ ~ 35 nm Ft ≈ 100 % ~ 30 nm Ft = 10 % Φ ~ 35 nm Ft = 80 % Φ~ 35 nm Ft = 60 % Φ ~ 30 nm Ft = 45 % 60 min. 45 min. 10 min. 30 min. 20 min. Isothermal annealing DSC at Tg + 50 °C • Various heat treatments Spherical crystallites + constant average size

  27. Crystallization / volume fraction Direct measurements through TEM imaging Crystal superposition and lack of contrast in bright field Bright field observation Dark field measurements of volume fraction Dark field observation Thickness measurement Collaboration: P. Donnadieu (LTPCM – INPG)

  28. Crystallization / volume fraction Direct measurements through TEM imaging • To calculate the real volume • fraction we need to have only • one crystal type : • Crystallite size • Crystallite nature Crystal superposition and lack of contrast in bright field Bright field observation Dark field measurements of volume fraction Dark field observation Thickness measurement TEM volume fraction of crystals depending on annealing time at Tg + 50 °C  annealing time ≤ 30 min. Collaboration: P. Donnadieu (LTPCM – INPG)

  29. Crystallization / volume fraction Direct measurements through XRD analysis • Crystals randomly oriented • Density constant (Dd / d < 1 %) XRD curves for the various samples

  30. Crystallization / volume fraction Direct measurements through XRD analysis • Crystals randomly oriented • Density constant (Dd / d < 1 %) Crystallized part 60 min. Amorphous part Amorphous Volume fraction of crystals Separation of the amorphous and crystalline contributions.

  31. Crystallization / volume fraction Validation of the method • 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)

  32. Crystallization / volume fraction Validation of the method • 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)

  33. Crystallization / volume fraction Validation of the method • 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) Large difference with predicted DSC transformed fraction (while sometimes used as crystalline fraction…)

  34. Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy DSC XRD TEM Microstructural characterisation Crystal volume fraction : OK How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  35. Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy DSC XRD TEM Microstructural characterisation Crystal volume fraction : OK How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  36. Effect of crystallization / room temperature Change in fracture mechanism : Fragmentation rather than shear fracture for Fv > 30 % • Fracture stress increases slightly and then falls ! Fracture stress as a function of annealing time Nanoindentation is even more interesting to study plasticity Journal of Alloys and Compounds (2006)

  37. Effect of crystallization / room temperature Al Amorphous Silica Plasticity map extracted from nanoindentation curves Journal of Materials Research (2007)

  38. Effect of crystallization / room temperature • Effect of crystallization • (Fv < 0.5) • Very limited variations of Rw and C/Eeq • Still sensitive to pressure Al Silica Plasticity map extracted from nanoindentation curves At room temperature: Effect on fracture rather than on deformation mechanisms Journal of Materials Research (2007)

  39. Aim: effect of crystallisation on mechanical properties at RT and HT Room Temperature High Temperature compression compression Mechanical characterisation methods nanoindentation DMA Validation for the amorphous alloy DSC XRD TEM Microstructural characterisation Crystal volume fraction : OK How the crystals contribute to change the mechanical response ? (rheology, elementary mechanism of deformation, reinforcement...) How the crystallisation modify the plasticity characteristics ?

  40. Effect of crystallization / high temperature Deformation ability is maintained up to large Fv • Two main effects of crystallization • Increase of viscosity • Promotion of non Newtonian behaviour Viscosity depending on strain rate The reinforcement for a given temperature depends on strain rate

  41. Effect of crystallization / high temperature • Effect of T : still just translation Still ability to draw master curves • Strain rate dependence of viscosity is the same for the various temperatures and Fv ~ 25 compression tests Viscosity curves : all temperatures and annealing times / translated along the two axes Similar mechanical behaviours in the investigated conditions (Fv, T and large strains)

  42. Effect of crystallization / high temperature ~ 200 curves Again able to draw master curves • Same elementary mechanism of deformation for the various temperatures and Fv DMA curves : all temperatures and annealing times / translated along the two axis THERMEC (2006)

  43. Effect of crystallization / high temperature The amorphous matrix seems responsible for the deformation Prediction of the reinforcement factor ( ) ? Similar mechanical behaviours in the investigated conditions (Fv, T and both small and large strains) Reinforcement depends on strain rate… Comparison performed in Newtonian regime

  44. Effect of crystallization/ high temperature / reinforcement • Prediction of R from mechanical models ? • Hard sphere dispersion in a viscous media : Krieger model T = Tg + 30 °C Reinforcement factor for various Fv (less than 30 %)

  45. Effect of crystallization/ high temperature / reinforcement • Prediction of R from mechanical models ? • Hard sphere dispersion in a viscous media : Krieger model T = Tg + 30 °C Krieger model Underestimate the reinforcement !! Reinforcement factor for various Fv (less than 30 %)

  46. Effect of crystallization/ high temperature / reinforcement Tg + 30°C T decreases Tg Various T • Prediction of R from mechanical models ? • Hard sphere dispersion in a viscous media : Krieger model Krieger model Underestimate the reinforcement !! Reinforcement factor for various Fv (less than 30 %) and temperatures Reinforcement depends on strain rate and temperature (simple mechanical models are not adapted)

  47. Effect of crystallization/ high temperature / reinforcement Still able to use an Arrhenius law Partially crystallized Newtonian viscosity Glass Activation energies in SLR measured by two ways Temperature ISMANAM (2006)

  48. Effect of crystallization/ high temperature / reinforcement Still able to use an Arrhenius law Partially crystallized Newtonian viscosity Glass Activation energies in SLR measured by two ways Temperature Reinforcement increases with temperature because: Decrease of viscosity is less rapid when crystals are present ISMANAM (2006)

  49. Effect of crystallization/ high temperature / activation energies Three possible reasons to explain the decrease of activation energy Direct change in composition of the residual glass ? NO ( ∆ Tg < 4 °C ) Direct contribution of crystal deformation ? NO ( TEM observations after deformation > 1.5 ) ISMANAM (2006)

  50. Effect of crystallization/ high temperature / activation energies Three possible reasons to explain the decrease of activation energy Direct change in composition of the residual glass ? Direct contribution of crystal deformation ? Influence of the coupling between matrix and crystals ? d Matrix layer perturbed by the proximity of crystals Small “flow channels” between crystallites Modification of matrix activation energy at crystal neighborhood

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