MODIFICATION OF AMORPHOUS Co-BASED METAL ALLOY BY SHOCK-WAVE LOADING

1. MODIFICATIONOF AMORPHOUS Co-BASED METAL ALLOY BY SHOCK-WAVELOADING A.Z.Bogunov, R.S.Iskhakov, V.I.Kirko, A.A.Kuzovnikov JSC « Pulse technologies » 660036, Krasnoyarsk, Russia, POB 26780, e-mail: limom1@yandex.ru L.V. Kirenskiy Institute of physics SB RAS, 660036, Krasnoyarsk, e-mail: rauf@iph.krasn.ru Siberian federal university, 660041, Krasnoyarsk, st. Svobodny, 62 1

2. Research Objectives Obtaining a Co-based massive metallic glass samples by dynamic compaction of powder Annealing the compacts in order to study them in three structural states: amorphous, metastable nanocrystalline; stable crystalline; Measurement of the shock adiabat of amorphous and stable crystalline samples; Measurement of the pressure profile in the shock wave front for the amorphous and stable crystalline material; Measurement of changes in the electric resistance of some amorphous ribbon during the shock loading Study of recovered samples after shock loading by X-ray diffraction, DTA; magnetic structure analysis, microhardness; The possibilities of practical application of the results.

3. Preparation of samples Detonator HE Shell Powder Container Base Pressure of compaction 5 GPa Grinding ribbon to powder Explosive compaction Quenchingfrom the melt Massive amorphous sample: Density 7,4 g/cm3 Porosity  0,2% Diameter 20 mm Thickness 3 mm

4. Manufacture metastable nanocrystalline and equilibrium crystalline samples Crystalline samples Amorphous alloy Metastable nanocrystalline Annealing4500С+GrindingCompaction Ribbon Co58Ni10Fe5Si11B16→ Powder Co58Ni10Fe5Si11B16→Compact Co58Ni10Fe5Si11B16 Annealing 5400С metastable CompactCo58Ni10Fe5Si11B16 → fcc Со + Со3(BSi) Shock loading up to 40 GPa Annealing 7300С crystalline CompactCo58Ni10Fe5Si11B16 → fcc Co + Co2B+Co2Si Annealing temperature based on DTA

5. Experimental assembly HE Copper plate 3 mm Manganin gauge Two layer Cu barrier 3mm+1mm Steel collar Sample ( impedance matching method) Pressure profile P16GPa Reflected shock wave Reflected unloading wave P14GPa Р t

6. Hugoniot compression curve of the amorphous alloyCoNiFeSiB P, GPa • Curve kink: • Elasto-plastic transition • Phase transition New phase There is no inflection on the shock adiabat of the stable crystalline samples Р = 13GPa Similar results for Zr-based alloy Initial phase T.Mashimo,H.Togo,Y.Zhang,Y.Kawamura. Material science and Engineering A449-451(2007) 264-268 V/V0 6

7. Р2=18 GPa Р1=13GPA Stable crystalline Amorphousalloy 1 s HE Pressure history on the front of the shock wave Cooper plate Barrier Manganin gauge in the samples Steel collar Experimental assembly Two-wave profile of a shock wave in the amorphous sample Р t

8. R/Rо,% Р R R Исходная фаза t Р, GPa Electric resistance measure during shock loading The ribbon of amorphous alloy Co70 Fe5Si10B15

9. X – ray diffraction of recovered samples Metastable nanocrystalline 20 GPa 5 GPa No measurable changing Amorphousalloy 20 GPa 5 GPa МоК - radiation

10. Microhardness of the recovered samples HVx102, GPa Metastablenanocrystalline Stable crystalline Amorphousalloy Р, GPa DTA of amorphous material has no change after shock loading ( P = 30 GPa)

11. М, Gs Bloch constant Magneticstructure analysis Мs B = const Ms1/2A-3/2 В Exchange interaction Аfcc-Co 2A hpc-Со 4 А Со3(B,Si) Structure characteristic Bloch law Ms – phase composition М(Т) = Мs (1 - ВТ3/2), A – close order (inter distance and number of magnetoactive atoms) Т 3/2, 103К 3/2

12. Мs, Gs Amorphous alloy Metastable nanocrystalline Stable crystalline Р, GPa No measurable changing Magnetic saturation – pressure dependence

13. Amorphousalloy Metastablenanocrystalline Ordering P, GPa Bx105, К -3/2 Constant Bloch - pressure dependence Disordering (phase transition) • fcc-Со hcp-Со: • Т  4000С; • High pressure; • Plastic deformation Stable crystalline

14. Discussion Elasto-plastic transition This transition was observed experimentally in shock wave loading amorphous alloys Amorphous alloys exhibit high values of HEL with subsequent loss of strength Changing the nature of deformation (shear band) could lead to disordering of the short-range order 2. fcc-Co  hcp-Co transition This transition was observed during the crystallization of the Co-based alloy under high pressure The irreversible transition can be quantitatively explained by changes of the magnetic characteristics for the amorphous and metastable (crystalline analogue) alloys, but the transition is not confirmed by structural method (X- Ray, DTA) Large volume changes on the shock adiabat - 12% There are no features at the Hugoniot of crystalline alloy like amorphous alloy

15. Сonclusion A kink on the Hugoniot compression curve and two-wave profile of the shock wave, which may indicate a phase transition, were found at the Co-based metallic glass compacts. The electrical resistance - pressure dependence of the amorphous Co-based ribbon shows a sharp decrease, which may be caused by phase transition. The features of the basic magnetic characteristics indicate possible transition of the fcc-Co close order to the hcp-Co close order at the amorphous and nanocrystalline states under shock loading. Amorphous alloys,which have reversible transformation with a large relative volume change, may be used as a medium for creating and maintaining the pressure after unloading (the method of dynamic-static compression)