Alloy by Synchrotron Radiation

Transcription

1 1 Analysis of Glass-forming Alloy by Synchrotron Radiation T. A. Başer /NIS Università degli Studi di Torino/ITALY European School-BMGs/ 13-1 Sept /Torino-ITALY

2 Fe-based Bulk Metallic Glasses with Y Addition Addition of large atoms, such as Y, is very helpful in terms of glass formation Y played the role of oxygen scavenger in Fe-Cr-Mo-C-B alloys, which led to the suppression of heterogeneous nucleation and improved glass formability. Ponnambalam V. and Poon Joseph S., J. Mater, Vol19, No.5, 13 () Glass formation in Fe-based alloy with Y addition is favored thermodynamically, resulting in an evident enhancement of GFA. Y effectively shifts the alloy composition from off-eutectic close a eutectic points. Lui Z. P., Liu C. T., Thompson J. R. and Porter W. D., Phys. R. Lett vol.9 no, 553-1, () European School-BMGs/ 13-1 Sept /Torino-ITALY

3 Heat Flow Fe 8 Cr 15 Mo 1.1 W /g Exothermic 1 Y C 15 B - as-cast sample Crystallisation Behaviour The crystallisation gives various overlapped exothermic peaks 1 C/min Temperature ( C) 8 The crystallisation products likely constitute a metastable mixture, as evidenced by the small exothermic peak OR It is caused by some residual amorphous structure. There is some residual amorphous fraction after crystallisation European School-BMGs/ 13-1 Sept /Torino-ITALY

4 ESRF/id11 water circulator Pt thermocouple inside of the stage Sample holder-linkam hot stage up to 1 C European School-BMGs/ 13-1 Sept /Torino-ITALY

5 5 Crystallisation Behaviour of Fe sample WAXS Results T i :5 ºC T f :1 ºC Scanning rate: 1 ºC/min ESRF/ID11 Fe 8 Cr 15 Mo 1 λ=.159 A 1 Y C 15 B as-cast Intensity θ 7 Temperature ( C) Increased by 1ºC! European School-BMGs/ 13-1 Sept /Torino-ITALY

6 Crystallisation Behaviour of Fe sample Fe 8 Cr 15 Mo Y C 15 B as-cast ºC/min T x 1 st crystallisation T 1 Amorphous phase Intensity Fully amorphous 1 st nd Temperature (ºC) Exothermic T nd crystallisation θ 1 Small exothermic peak T x (ºC) T 1 (ºC) T (ºC) DSC LINKAM ΔT European School-BMGs/ 13-1 Sept /Torino-ITALY

7 7 RIETVELD REFINEMENT Paracrystal Model By comparing partial radial distribution functions of metallic glasses with those of their crystalline counterparts, we attempt to give an answer to the question as to which similarities exist between the short range atomic order found in amorphous structures and that found in crystals. For this purpose the concept of paracrystallinity is used.the atomic size play a part only in geometrical scaling factors.crystal structures used in the calculations of RDFs for para-crystals. Behind the idea of para-crystal model that crystal size is reduced, grain is not needed anymore. Sietsma J. And Thijsse B.,J. Non-Cryst. Solids 11 (1988) Rietveld Quantitative amorphous content analysis The method derives the amorphous content from the small over-estimation of an internal crystalline standart in a Rietveld Refinement of an appropriate mixture. This approach focused on crystal fractions. There is no explanation of amorphous fraction. There is no physical information about background. J. Appl. Cryst. 3, (1), 19-. European School-BMGs/ 13-1 Sept /Torino-ITALY

8 8 Intensity Rietveld Refinement (by Maud) Fully Amorphous Sample θ total experimental background paracrystal model silica glass 8 Fe 3 C is used as a paracrystalline The same calculation was performed, but this calculation was not in better agreement with the experimental data. Silica glass is used to eliminate the effect of quartz capilary European School-BMGs/ 13-1 Sept /Torino-ITALY

9 Intensity 3 After 1 st Crystallisation Event total experimental background paracrystal model Cr 3 C silica glass 8 8 Intensity After nd Crystallisation Event total experimental background paracrystal Cr 3 C +Fe 3 Mo 3 C silica glass θ θ Cr 3 C phase occured during 1 st crystallisation Fe 3 Mo 3 C phase occured during nd crystallisation Amorphous phase fraction:.81 Amorphous phase fraction:.13 European School-BMGs/ 13-1 Sept /Torino-ITALY

10 total 8 experimental background 7 Cr 3 C 8 Intensity 5 3 Rietveld Refinement (by Gsas) After 1 st Crystallisation Event total 8 experimental background Cr 3 C and Fe 3 Mo 3 C 8 Intensity After nd Crystallisation Event θ θ Cr 3 C phase occured during 1 st crystallisation Fe 3 Mo 3 C phase occured during nd crystallisation European School-BMGs/ 13-1 Sept /Torino-ITALY

11 11 Comparison pattern of crystals using by maud and gsas Intensity After 1 st Crystallisation Event maud gsas 8 Cell parameters Phase Quantity Crystal Size Micro Strain Cr 3 C a=1.773 A (maud) a=1.7 A (gsas).51 (maud) A (maud).5 (maud) Cr 3 C phase has been identified by paracrystalline model θ Cr 3 C phase has been identified without paracrystalline model European School-BMGs/ 13-1 Sept /Torino-ITALY

12 1 After nd Crystallisation Event Intensity θ maud gsas Cell parameters Phase Quantity Crystal Size Micro Strain Cr 3 C a=1.78 A (maud) a=1.753 A (gsas) Fe 3 Mo 3 C a=11.17 A (maud) a= A (gsas).315 (maud).1 (maud).73 A (maud) A (maud).5 (maud).11 (maud) Cr 3 C and Fe 3 Mo 3 C phases have been identified by paracrystalline model Cr 3 C and Fe 3 Mo 3 phases have been identified without paracrystalline model European School-BMGs/ 13-1 Sept /Torino-ITALY

13 13 Small Peak T (ºC) DSC 975 WAXS ΔT C/min Heat Flow Exotherm ic Tem perature ( C) 8 It is caused by some residual amorphous structure. There is some residual amorphous fraction after nd crystallisation Fe.3 Cr 5 Co 5 Mo 1.8 Mn 11. C 15.8 B 5.9 (Fe.3 Cr 5 Co 5 Mo 1.8 Mn 11. C 15.8 B 5.9 ) 98.5 Y 1.5 Lui Z. P., Liu C. T., Thompson J. R. and Porter W. D., Phys. Rev. 9 (), Ponnambalam V. and Poon Joseph S., J. Mater. Res, 19, (), 13. European School-BMGs/ 13-1 Sept /Torino-ITALY

14 1 Between 1 st and nd Crystallisation (by Gsas) lattice constant vs. temperature a, Cell Parameter (A ) st crystallisation Temperature ( C) nd crystallisation 8 Temperature( C) Cell Parameter (A ) As temperature increase lattice constants increase OR Change of composition. If an element in (Fe,Cr) or (C,B) changed, they might be change the lattice constant European School-BMGs/ 13-1 Sept /Torino-ITALY

15 15 Conclusions Paracrystal and Quantitative Models are both suitable with ESRF data These approaches are also suitable for composites The open problem is what is the phase to select for paracrystalline model? Small peak which was observed after crystallisation caused by some residual amorphous structure. There is some residual amorphous fraction after crystallisation European School-BMGs/ 13-1 Sept /Torino-ITALY

16 1 Cu 5 Zr 5 binary system and Cu 5 Zr 5 with Al or Nb additions!as the ratio of shear modulus μ to bulk modulus B increases or poison ratio ν decreases, the material becomes brittle A.L. Greer, Y. Zhang, submitted paper as part of the proceedings of ISMANAM, Paris, -7 July 5!Minor additions of Al increase the glass-forming ability: with addition of at. % Al to Cu 5 Zr 5 W.H. Wang, J. J. Lewondowski and A. L. Greer, J. Mater. Res., Vol, No9, Sep5. European School-BMGs/ 13-1 Sept /Torino-ITALY

17 17 Melting Behaviour of Cu T Cu 5 Zr 5 5 master alloy- WAXS Results ESRF/ID11 λ=.159 A runs were performed t yirmibes yirmi onbes on bes S (nm) -1 European School-BMGs/ 13-1 Sept /Torino-ITALY

18 18 Melting Behaviour of Cu Results Cu 8 Zr 8 Al Al master alloy- WAXS ESRF/ID11 λ=.159 A S (nm) -1 European School-BMGs/ 13-1 Sept /Torino-ITALY

19 19 Melting Behaviour of Cu Results Cu 8 Zr 8 Nb ESRF/ID11 Nb master alloy- WAXS λ=.159 A S (nm) -1 European School-BMGs/ 13-1 Sept /Torino-ITALY

20 Phase identification on selected pattern (CuZr master alloy) ( ) Cu 1 Zr 7 ( ) CuZr cubic ( ) CuZr ( ) CuZr monoclinic basic (O) CuZr monoclinic super 8 Binary Phase Diagram of Cu-Zr Intensity During solidification During first melting First pattern θ Cu Zr European School-BMGs/ 13-1 Sept /Torino-ITALY

21 Acknowledgements: A. Reza Yavari M. Stoica K. Hajlaoui J. Das M. Bostrom Thank you for your attention!