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

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Presentation on theme: "Comportement mécanique des verres métalliques massifs - Effet dune cristallisation partielle Sous la direction de : Jean-Jacques Blandin Sébastien Gravier."— Presentation transcript:

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

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

3 3 Cooling a metal Crystallization Temperature Volume TmTm Liquid state Solid state Conventional solidification

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

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

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

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

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

9 9 Room temperature Elements Zr TiCu Ni Be Atomic % BMG studied in this thesis Vit1 (T g = 365 °C )

10 10 E corresponding crystalline alloys + f = 1830 MPa ( 1 %) e elast 0.02 Macroscopic brittleness Compression tests at room temperature on a BMG Macroscopic brittleness but local plasticity E f Room temperature elast BMG studied in this thesis Vit1 (T g = 365 °C ) Elements Zr TiCu Ni Be Atomic % Microscopic plasticity Fracture surface

11 11 Nanoindentation loading and unloading curves Room temperature L h Loading curve : L = C h 2 Unloading curve: ( Irreversible Work ratio ) R W = W irr / W tot Collaboration: L. Charleux ( INP-Grenoble )

12 12 Loading curve : L = C h 2 Unloading curve: ( Irreversible Work ratio ) R W = W irr / W tot Nanoindentation loading and unloading curves W tot W irr Room temperature > Silica Glass 40 % < Aluminium 100 % Suggest many dissipative events ! = 67 %

13 13 Nanoindentation loading and unloading curves W tot W irr Materials Science and Engineering A (2006) SdSd Room temperature Loading curve : L = C h 2 Unloading curve: ( Irreversible Work ratio ) R W = W irr / W tot > Silica Glass 40 % < Aluminium 100 % Suggest many dissipative events ! = 67 % AFM measurements : reduced Young modulus : E eq

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

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

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

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

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

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

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

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

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

23 23 Dynamic Mechanical Analysis (DMA) : Sinusoidal small strain tests Frequency scans at various fixed temperatures T High temperature Collaboration: Jean–Marc Pelletier GEMPPM, INSA Dissipative part of the deformation : Construction of a master curve Elementary mechanism of deformation independent of T Apparent activation energy ~ 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 Phase difference between applied stress and strain

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

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

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

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

28 28 To calculate the real volume fraction we need to have only one crystal type : Crystallite size Crystallite nature Crystallization / volume fraction annealing time 30 min. Direct measurements through TEM imaging Dark field observationThickness measurement Bright field observation Crystal superposition and lack of contrast in bright field Dark field measurements of volume fraction 0 min.10 min.20 min.30 min. Fv (%) TEM volume fraction of crystals depending on annealing time at Tg + 50 °C Collaboration: P. Donnadieu (LTPCM – INPG)

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

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

31 31 Amorphous10 min.20 min.30 min. Volume fraction (%) TEM XRD 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) Validation of the method Crystallization / volume fraction

32 32 Amorphous10 min.20 min.30 min.45 min.60 min. Volume fraction (%) TEM ?? XRD Validation of the method 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)

33 33 Amorphous10 min.20 min.30 min.45 min.60 min. Volume fraction (%) TEM ?? XRD DSC Ft (%) Validation of the method Large difference with predicted DSC transformed fraction (while sometimes used as crystalline fraction…) 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)

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

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

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

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

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

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

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

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

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

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

44 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 45 Effect of crystallization / high temperature / reinforcement Underestimate the reinforcement !! Prediction of R from mechanical models ? Hard sphere dispersion in a viscous media : Krieger model T = Tg + 30 °C Krieger model Reinforcement factor for various Fv (less than 30 %)

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

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

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

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

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

51 51 Effect of crystallization / high temperature / activation energies 1 nm 3 nm 5 nm Fraction of amorphous matrix perturbed because of proximity of crystals Effect of various interface thickness coupling between matrix and crystals (crystal size 30 nm) ?

52 52 Effect of crystallization / high temperature / activation energies Fraction of amorphous matrix perturbed because of proximity of crystals Nanometer crystallites Large fraction of the remaining amorphous matrix can be disturbed by crystal proximity coupling between matrix and crystals (crystal size = 30 nm) ? 1 nm 3 nm 5 nm Distance between crystallites effect Visualization of the small distances between crystals : Fv = 30 % 30 nm Effect of various interface thickness

53 53 Validation of new methods - compression / nanoindentation fracture vs. plasticity calculation of both the pressure sensitivity and the yield stress - compression / DMA large strain interval deformation mechanism at small strains vs. large strain mechanism - TEM / XRD Measurements of the volume fraction of crystals Main conclusions

54 54 Main conclusions Open questions on the effect of crystallization - At room temperature: Does the crystals modify the plasticity characteristics ? Modify the fracture (fragmentation for Fv > 30 %) Limited modification of the plastic mechanism Small variation of Rw Still a pressure sensitivity - At high temperature: How the crystals contribute to change the mechanical response ? Deformation mechanism seems similar whatever Fv (< 50 %), the strain or the temperature Promotion of non Newtonian behavior Reinforcement effect depends on temperature

55 55 Perspectives / scientific Modelling the high temperature deformation Similarity between deformation mechanisms for small strain and large strain Interest of the definition of the elementary mechanism of deformation

56 56 Perspectives / scientific Modelling the high temperature deformation Similarity between deformation mechanisms for small strain and large strain Need to go from elementary deformation to macroscopic deformation Flow defect concentration Interest of the definition of the elementary mechanism of deformation Elementary shear mechanism of Argon Flow defect

57 57 Perspectives / scientific Study of the size effect of nanocrystals One comparison point already achieved: Fv = 16% + Mean crystallite size = 7 nm Fv = 17% + Mean crystallite size = 30 nm and No differences observed … … up to now !!

58 58 Perspectives / technological Interest of bulk metallic glasses / metallic alloys composites Patent in progress 10 mm Advanced Engineering Materials (2006) 1 mm Al-alloy Vit1 Interesting mechanical properties… Fracture stress + Plasticity + High interface shear stress Co-deformed multimaterials designed thanks to the deformation ability of the glass in the SLR Resistance of metallic glass + ductility of metallic alloy Push out tests 1 mm Al-alloy Vit1

59 59 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

60 60

61 61

62 62 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 Point not aborded Materials Science and Engineering A (2006)

63 63 Link between localized deformation and homogeneous flow ? Characterization of the localized deformation Influence of a temperature increase Transition with homogeneous flow Compression test at room temperature: Zr based BMG with plasticity (collaboration with Shanghai university) plastic > 0.07 Perspectives / scientific

64 64 Poisson ratio … deformation mechanism Yoshida et al., JMR 2005 Lewandowski et al., Phil. Mag Pd

65 65 Crystallisation Three crystallization events may occur at higher temperature… Analyze here the two first crystallization peaks DSC scan at 10°/min. / amorphous sample T g 365 °C T p1 = 438 °C T p2 = 457 °C T p3 = 505 °C Isothermal Annealing at 410°C

66 66 DMA / Activation energy Activation energy: T Tg : Q 450 kJ/mol DMA / Temperature scan

67 67 ISMANAM (2006) Activation energies in SLR measured by two ways Effect of crystallization : Newtonian Viscosity Amorphous Fv = 32 % Influence of the temperature on the reinforcement

68 68 Effect of the deformation on the crystallization Materials Science and Engineering A (2006) No visible influence of the deformation on the crystallization Reinforcement factor as a function of time. Cristallisation proceed while deforming

69 69 Effect of the deformation on the crystallization Materials Science and Engineering A (2006) DRX on two samples DSC on four samples No visible influence of the deformation on the crystallization

70 70 Deformed Effect of the deformation on the crystallization Materials Science and Engineering A (2006) No visible influence of the deformation on the crystallization

71 71 High temperature Mechanism Multiatomic approach of the high temperature deformation Multiatomic deformation mechanism High apparent activation energy Shear model of Argon Resistance of the surrounding Q apparent = Q (interfacial shear resistance) + Q (mechanical resistance of the surrounding)

72 72 High temperature Mechanism Evolution of the activation energy Glassy state Supercooled liquid Liquid state TgTg TfTf E act : T < T g E act T > T f E act T > T g Continuous decrease ? Mechanical resistance of the surrounding is decreasing

73 73 High temperature Mechanism Defect concentration evolution H f = 14 kJ /mol S f = 6 J /mol/°C

74 74 Co-extruded materials

75 75 Co-extruded materials

76 76 Co-extruded materials

77 77 Co-extruded materials

78 78 Co-extruded materials


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