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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_at_yandex.ru L.V. Kirenskiy Institute of
physics SB RAS, 660036, Krasnoyarsk, e-mail
rauf_at_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.

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Preparation of samples
Grinding ribbon to powder
Explosive compaction
Quenching from the melt
Massive amorphous sample Density 7,4
g/cm3 Porosity ? 0,2 Diameter 20 mm Thickness 3
mm
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Manufacture metastable nanocrystalline and
equilibrium crystalline samples
Annealing temperature based on DTA
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( impedance matching method)

Pressure profile
P ? 16 GPa
Reflected shock wave
Reflected unloading wave
P ? 14 GPa
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Hugoniot compression curve of the amorphous alloy
CoNiFeSiB
P, GPa

• Curve kink
• Elasto-plastic transition
• Phase transition

New phase
There is no inflection on the shock adiabat of
the stable crystalline samples
? 13 GPa
Initial phase
Similar results for Zr-based alloy
T.Mashimo,H.Togo,Y.Zhang,Y.Kawamura. Material
science and Engineering A449-451(2007) 264-268
V/V0
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Pressure history on the front of the shock wave

• Experimental assembly

HE
Cooper plate
Barrier
Manganin gauge in the samples
Steel collar
Two-wave profile of a shock wave in the amorphous
sample
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Electric resistance measure during shock loading
The ribbon of amorphous alloy Co70 Fe5Si10B15
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X ray diffraction of recovered samples
Metastable nanocrystalline
20 GPa
5 GPa
No measurable changing
Amorphous alloy
20 GPa
5 GPa
???? - radiation
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Microhardness of the recovered samples
DTA of amorphous material has no change after
shock loading ( P 30 GPa)
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Magnetic structure analysis
?, Gs
Bloch constant
?s
B const Ms1/2 A-3/2
?
Exchange interaction
? fcc-Co ?2A hpc-?? ?4 ? ??3(B,Si)
Structure characteristic
Bloch law
Ms phase composition
?(?) ?s (1 - ??3/2),
A close order (inter distance and number of
magnetoactive atoms)
? 3/2, 103? 3/2
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Magnetic saturation pressure dependence
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Constant Bloch - pressure dependence
Bx105, ? -3/2
Disordering (phase transition)

• fcc-?? ? hcp-??
• ? ? 4000?
• High pressure
• Plastic deformation

Stable crystalline
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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

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?onclusion

• 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)