This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
11
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:
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
7
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
8
Electric resistance measure during shock loading
The ribbon of amorphous alloy Co70 Fe5Si10B15
Исходная фаза
Р, GPa
R/Rо,%Р
R
t
R
9
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)
11
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
12
Magnetic saturation – pressure dependence
No measurable changing
Amorphous alloy
Metastable nanocrystalline
Stable crystalline
Мs, Gs
Р, GPa
13
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
15
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)