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MODIFICATION OF AMORPHOUS Co-BASED

METAL ALLOY BY SHOCK-WAVE LOADING

A.Z.Bogunov, R.S.Iskhakov, V.I.Kirko,

A.A.Kuzovnikov

JSC « Pulse technologies »660036, Krasnoyarsk, Russia, POB 26780, e-mail:

limom1@yandex.ruL.V. Kirenskiy Institute of physics

SB RAS, 660036, Krasnoyarsk, e-mail: rauf@iph.krasn.ru Siberian federal university,

660041, Krasnoyarsk, st. Svobodny, 62

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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.

Preparation of samples

Grinding ribbon to powder

Explosive compaction

Massive amorphous sample:Density 7,4 g/cm3

Porosity 0,2%Diameter 20 mmThickness 3 mm

Quenching from the melt

Detonator HE

Powder

Base

Shell

Pressure of compaction 5 GPa

Container

Manufacture metastable nanocrystalline and equilibrium

crystalline samples

Annealing temperature based on DTA

Metastable nanocrystalline

Amorphous alloy

Crystalline samples

Annealing 4500С+Grinding Compaction Ribbon Co58Ni10Fe5Si11B16 → Powder Co58Ni10Fe5Si11B16 → Compact Co58Ni10Fe5Si11B16 Annealing 5400С metastable Compact Co58Ni10Fe5Si11B16 → fcc Со + Со3(BSi) Annealing 7300С crystalline Compact Co58Ni10Fe5Si11B16 → fcc Co + Co2B+Co2Si

Shock loading up to 40 GPa

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Hugoniot compression curve of amorphous and crystalline samples

Experimental assembly

Sample

HE

Copper plate 3 mmTwo layer Cu barrier 3mm+1mm

Steel collar

Manganin gauge

Рt

Pressure profile

P 14 GPa

P 16 GPaReflected shock wave

Reflected unloading wave

( impedance matching method)

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Hugoniot compression curve of the amorphous alloy CoNiFeSiB

New phase

Р = 13 GPa

Curve kink:•Elasto-plastic transition•Phase transition

Initial phase

There is no inflection on the shock adiabat of the stable crystalline samples

V/V0

P, GPa

T.Mashimo,H.Togo,Y.Zhang,Y.Kawamura. Material science and Engineering A449-

451(2007) 264-268

Similar results for Zr-based alloy

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Pressure history on the front of the shock waveExperimental assembly

Two-wave profile of a shock wave in the amorphous sample

Manganin gauge in the samples

Рt

Stable crystalline Amorphou

s alloy

1 s

Р1=13 GPA

Р2=18 GPa

HE

Cooper plate

BarrierSteel collar

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Electric resistance measure during shock loading

The ribbon of amorphous alloy Co70 Fe5Si10B15

Исходная фаза

Р, GPa

R/Rо,%Р

R

t

R

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X – ray diffraction of recovered samples

Amorphous alloy

Metastable nanocrystalline

No measurable changing

20 GPa

20 GPa

5 GPa

5 GPa МоК - radiation

Microhardness of the recovered samples

0 10 20 30 40 50

1100

1200

1300

1400

1500

1600

Amorphous alloy

Metastable nanocrystalline

Stable crystalline

Р, GPa

HV x102, GPa

DTA of amorphous material has no change after shock loading ( P = 30 GPa)

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Magnetic structure analysis

М(Т) = Мs (1 - ВТ3/2),

Bloch law

Мs

ВB = const Ms

1/2 A-3/2

Bloch constant

Exchange interactionА fcc-Co 2A hpc-Со 4 А Со3(B,Si)

Structure characteristicMs – phase composition

A – close order (inter distance and number of magnetoactive atoms)

М, Gs

Т 3/2, 103К 3/2

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Magnetic saturation – pressure dependence

No measurable changing

Amorphous alloy

Metastable nanocrystalline

Stable crystalline

Мs, Gs

Р, GPa

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Constant Bloch - pressure dependence

Disordering (phase transition)fcc-Со hcp-Со:

•Т 4000С; • High pressure; •Plastic deformation

Bx105, К -3/2

Metastable nanocrystalline

Amorphous alloy

Ordering

P, GPa

Stable crystalline

Discussion1. 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

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Сonclusion1. 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.

2. The electrical resistance - pressure dependence of the amorphous Co-based ribbon shows a sharp decrease, which may be caused by phase transition.

3. 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.

4. 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)