Mechanical behavior of Zr-based bulk metallic glasses
Bulk metallic glasses have a very high corrosion resistance and mechanical strength. Bulk metallic glasses show elastic-perfectly plastic behavior with an extended region of elastic strain (≈ 2%). But at room temperature their macroscopic plasticity is weak even though a local plastic strain is obse...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
2008
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| Цитувати: | Mechanical behavior of Zr-based bulk metallic glasses / S. Nowak, P. Ochin, A. Pasko, S. Guérin, Y. Champion // Проблемы прочности. — 2008. — № 1. — С. 167-170. — Бібліогр.: 10 назв. — англ. |
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irk-123456789-484172013-08-19T16:13:08Z Mechanical behavior of Zr-based bulk metallic glasses Nowak, S. Ochin, P. Pasko, A. Guerin, S. Champion, Y. Научно-технический раздел Bulk metallic glasses have a very high corrosion resistance and mechanical strength. Bulk metallic glasses show elastic-perfectly plastic behavior with an extended region of elastic strain (≈ 2%). But at room temperature their macroscopic plasticity is weak even though a local plastic strain is observed in shear bands. A relaxation analysis allowed studying micro-mechanisms of plastic deformation and estimating the apparent activation volume (≈ 2000 ³). Высокопрочные стекла на основе металлов имеют очень высокие характеристики коррозионной устойчивости и механической прочности. Их деформирование является абсолютно упругопластическим с протяженным участком упругости (≈ 2%). Однако при комнатной температуре их макропластичность проявляется слабо, несмотря на наличие локальных пластических деформаций в полосах скольжения. Анализ релаксации напряжений позволил исследовать микромеханизмы пластического деформирования и оценить значение объема активации (≈ 2000 ³). 2008 Article Mechanical behavior of Zr-based bulk metallic glasses / S. Nowak, P. Ochin, A. Pasko, S. Guérin, Y. Champion // Проблемы прочности. — 2008. — № 1. — С. 167-170. — Бібліогр.: 10 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/48417 539.4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Научно-технический раздел Научно-технический раздел Nowak, S. Ochin, P. Pasko, A. Guerin, S. Champion, Y. Mechanical behavior of Zr-based bulk metallic glasses Проблемы прочности |
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Bulk metallic glasses have a very high corrosion resistance and mechanical strength. Bulk metallic glasses show elastic-perfectly plastic behavior with an extended region of elastic strain (≈ 2%). But at room temperature their macroscopic plasticity is weak even though a local plastic strain is observed in shear bands. A relaxation analysis allowed studying micro-mechanisms of plastic deformation and estimating the apparent activation volume (≈ 2000 ³). |
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Article |
| author |
Nowak, S. Ochin, P. Pasko, A. Guerin, S. Champion, Y. |
| author_facet |
Nowak, S. Ochin, P. Pasko, A. Guerin, S. Champion, Y. |
| author_sort |
Nowak, S. |
| title |
Mechanical behavior of Zr-based bulk metallic glasses |
| title_short |
Mechanical behavior of Zr-based bulk metallic glasses |
| title_full |
Mechanical behavior of Zr-based bulk metallic glasses |
| title_fullStr |
Mechanical behavior of Zr-based bulk metallic glasses |
| title_full_unstemmed |
Mechanical behavior of Zr-based bulk metallic glasses |
| title_sort |
mechanical behavior of zr-based bulk metallic glasses |
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Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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2008 |
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Научно-технический раздел |
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http://dspace.nbuv.gov.ua/handle/123456789/48417 |
| citation_txt |
Mechanical behavior of Zr-based bulk metallic glasses / S. Nowak, P. Ochin, A. Pasko, S. Guérin, Y. Champion // Проблемы прочности. — 2008. — № 1. — С. 167-170. — Бібліогр.: 10 назв. — англ. |
| series |
Проблемы прочности |
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| first_indexed |
2025-07-04T08:51:17Z |
| last_indexed |
2025-07-04T08:51:17Z |
| _version_ |
1836705726074978304 |
| fulltext |
UDC 539. 4
M e c h a n ic a l B e h a v io r o f Z r -B a s e d B u lk M e ta l l ic G la s se s
S. N ow ak ,1a P . O ch in ,1b A . P a sk o ,1 S. G u érin ,1 and Y . C h am p ion 1’0
1 ICMPE-CNRS UMR7182, Université Paris, Vitry-sur-Seine, France
a nowak@icmpe.cnrs.fr, b ochin@icmpe.cnrs.fr, c champion@icmpe.cnrs.fr
Bulk metallic glasses have a very high corrosion resistance and mechanical strength. Bulk metallic
glasses show elastic-perfectly plastic behavior with an extended region o f elastic strain (~ 2%). But
at room temperature their macroscopic plasticity is weak even though a local plastic strain is
observed in shear bands. A relaxation analysis allowed studying micro-mechanisms o f plastic
deformation and estimating the apparent activation volume (~ 2000 Â3).
K eyw ords: bulk m etallic glasses, com pression test, stress relaxation, m echanical properties.
Introduction . Amorphous m etallic alloys also called m etallic glasses are characterized
by absence o f atom ic long-range order. B ulk m etallic g lasses (B M G ) exhibit a very h igh
strength ( ~ 1,6 GPa) and elasticity ( ~ 2%). H ow ever, at room temperature, they have low
ductility because of the localization of the plastic strain w hich is concentrated in a few thin
shear bands. Deform ation behavior of B M G s is com pletely different than crystallized metals
(no dislocation). Spaepen [1 ] and A rgon [2 ] describe the deformation as the result o f jumps
o f respectively single-atom or group o f atoms in “h o les” (free volum es) large enough.
Zr-based B M G have a h igh GFA (G lass Form ing A bility) and particularly the alloy
Zr57Cu20A l10Ti8N i5 w hich is the studied alloy in this paper.
B M G S yn th esis and C h aracteriza tion . Initially, the five pure elem ents are m elted
by electrom agnetic induction heating in a w ater-cooled copper crucible under He
atm osphere (Fig. 1a). From 20 to 35 g o f B M G s are obtained by re-m elting using
electrom agnetic levitation under He atmosphere and casting into a copper m old (Fig. 1b).
D ifferent shapes o f sam ples are produced, depending on the subsequent use:
2 0 X 35X 5 m m sheets for com pression tests, rods w ith 10 m m diameter for transm ission
electron m icroscopy analysis and w edge shaped sam ples for the evaluation o f the glass
form ing ability (GFA).
For com pression tests, rectangular shaped sam ples, 4X 4 m m o f cross-sectional area
and 6 m m height, were m achined and then polished.
X -ray diffraction and TEM analysis were carried out to control the amorphous state
o f the as-cast sam ples (presence o f broad diffuse peaks for X R D , and diffuse rings for
TEM).
The glass transition temperature (Tg = 660 K) and the crystallization temperature
(Tx = 719 K) o f the alloy were m easured using differential scanning calorimeter (DSC)
and the liqu idus tem perature T i = 1156 K) w as m easured u sin g DTA . H eating rate o f
20 K /m in w as applied for each analysis.
M ech an ica l B ehavior. U niaxial com pression test under quasi-static loading at room
temperature w as performed. B M G exhibits a perfect elastic deformation behavior follow ed
by a catastrophic brittle fracture w ith no y ield ing (Fig. 2). The fracture stress is 1634 MPa
and the region o f elastic strain is extended (~ 2%). Though m acroscopic p lasticity is low,
local plastic strain is observed in shear bands (Fig. 3).
Typical m orphology o f the fracture surface o f a BM G , at room-temperature in
com pression, is show n in Fig. 4. Veins w ith liquid droplets were observed in the entire
fracture surface. It w as demonstrated that shear localization induces a temperature rise
(more than 900°C at the final-fracture m om ent, i.e ., higher than Ti ) and that deform ation
is then related to a local decrease o f the v iscosity in the shear bands [3].
© S. N O W A K , P. O C H IN , A. PA SK O , S. GUÉRIN, Y. CHAMPION, 2008
ISSN 0556-171X. Проблемыг прочности, 2008, N 1 167
mailto:nowak@icmpe.cnrs.fr
mailto:ochin@icmpe.cnrs.fr
mailto:champion@icmpe.cnrs.fr
S. Nowak, P. Ochin, A. Pasko, et al.
Fig. 1
true strain (%)
Fig. 2
Fig. 1. (a) water-cooled copper crucible (b) electromagnetic levitation.
Fig. 2. Stress-strain curve of the Zr57Cu20A l10N i8Ti5 BMG deformed at room temperature at a strain
rate o f 2 - 10_5 s_1.
Fig. 3 Fig. 4
Fig. 3. View o f free surface, parallel to the compression direction, with visible shear bands. Shear
band thickness is about 20 nm [5].
Fig. 4. Fracture surface with veins and liquid droplets (insert).
The fracture angle w as measured for tw o samples: one w as 41° (Fig. 5), the other 45°.
These values indicate that B M G fo llow s the M ohr-C oulom b criterion for plastic yielding
in com pression. This behavior is observed for m any BM G , such as Zr574C u164N i82A l10
[4].
= 41°
Fracture
surface
Fig. 5. Fractured sample.
Stress R elaxation A n alysis . A relaxation test w as perform ed at room temperature to
approach the m icrom echanism s o f deformation. In literature, m ost experim ents were
conducted at temperatures close to Tg [1, 6], B M G having hom ogeneous deform ation at
these temperatures. In our experim ent, an attempt is m ade to exam ine the localized
168 ISSN 0556-171X. npoÖÄeubi npounocmu, 2008, N 1
Mechanical Behavior o f Zr-Based Bulk Metallic Glasses
deform ation in shear bands. R elaxation is a m ethod allow ing the m easurem ent o f the
rheologic and the m echanistic parameters w ithout failure o f the sam ple and at a
m acroscopic scale (in contrast to the nano-indentation investigating confine plasticity).
The sam ple is loaded w ith a strain rate o f £ = 5 - 1 0 5 s 1. The displacem ent o f the
cross head o f the testing m achine is stopped just before the catastrophic failure o f the
sample. The total deform ation is remained constant until the end o f the experim ent
(~ 160,000 s). Consequently, since total deform ation is the result o f plastic and elastic
deformation:
elastic ‘ (1)
The shear stress variation as a function o f tim e is plotted in Fig. 6. Three domains
are defined to describe the curve. B etw een 300 s (onset o f the relaxation) and 8000 s, the
stress decreases slow ly (A r max = 7 M Pa) fo llow ing the classical logarithm ic relation.
Then, after a transitory plateau, the curve g lobally increases until 100,000 s and finally
stabilizes in the third part.
ii in
♦ ц — 1 ._ _ frj-« ....... - , ._ ►
I С ! Probably shear
bands
form ationлX
о
-1
-2
ra
Cl -3
-4t-1
« -5
-6
-7
-8
0 3.4-10" 6.8 10* 110" 1.4 10'
time (s)
Fig. 6. Plot o f the shear stress variation as a function o f time.
I. The first dom ain fo llow s the logarithm ic function [7]:
Аг = г - г о = - y - ln ^ + C j , (2 )
where r is applied shear stress, r 0 is applied shear stress at the beginning o f the
relaxation, t is tim e, Vapp is apparent activation volum e, C is tim e factor, k is
Boltzm ann constant, and T absolute temperature. Vapp is the atom ic volum e involved in
an elem entary therm ally activated event. A t the onset o f the relaxation, the slope is almost
infinite and Vapp equal to zero. Then the curve can be perfectly fitted betw een 1000 and
3500 s by the logarithmic relation and the activation volum e Vapp is estim ated to 2000 A 3
(corresponding to 1 5 0 0 , w here O is the average atom ic volum e), w hich is reasonable
compared to h igh temperature m easurem ent [8].
II. A n increase o f r is observed, w hich is probably related to an energy release.
Such behavior is rather unusual. It w as verified that it w as not in relation w ith experim ent
artifact: stress variations induced by the m achine w ere m easured as neglig ib le compared
w ith the sam ple relaxation. M oreover, experim ents are perform ed in a room w ith constant
temperature and the system (sam ple-m achine) dilatation cannot be taken into account to
explain the phenom enon.
ISSN 0556-171X. Проблемы прочности, 2008, № 1 169
S. Nowak, P. Ochin, A. Pasko, et al.
So the change betw een dom ain I and II could be related to the variations in
micro-structure w hich is m ost lik ely a crystallization in shear bands [9]. A t T > Tg , N ieh
et al. [10] consider amorphous phase as a N ew tonian fluid and nanocrystalline particles as
having a superplastic behavior. The plastic deform ation strain rate is consequently
expressed by
y plastic ~ (1 _ f v Jy am f vy cryst ~ (1 _ f v )Ar + f v B , (3)
where f v is volum e fraction o f the crystalline phase, A and B are material constants,
y am and y cryst strain rates caused by the am orphous and the crystalline phase,
respectively , and r the applied flow stress.
Though experim ent is carried out at room temperature, deform ation occurring in
shear bands w here temperature rises should be described consisten tly by Eq. (3).
Consequently, the plastic deformation induces a decrease o f the applied stress. Nevertheless
the microstructure variation could be at the origin o f an internal stress release. The
measured stress w hich increases g lobally w ould be the sum o f the internal stress and the
applied stress.
III. Finally, the stress reaches a value threshold, m eaning no longer plastic
deform ation.
C onclusions. B M G s are produced by rapid cooling o f a m etallic alloy, avoiding
atom ic long-range order. That g ives specific properties to the material like no ductility
because o f the localization o f the plastic strain in shear bands. Stress relaxation allow ed
estim ating an apparent activation volum e associated to a p lastic deform ation and
observing an evolution o f deform ation m ode involving m ost likely a partial crystallization
phenom enon.
Acknowledgments. This work was supported by the DGA within the framework o f a “Recherche
Exploratoire et Innovation” (REI No. 05C0145) under the contract No. 0634030004707565 for the
PHD of one o f the authors (SN). The authors are also grateful to J. L. Bonnentien, A. Valette, and
M.-F. Trichet for technical support.
1. F. Spaepen, Acta Metall., 25, 407 (1977).
2. A. S. Argon, Acta Metall., 27, 47 (1979).
3. B. Yang, P. K. Liaw, G. Wang, et al., Intermetallics, 12, 1265 (2004).
4. R. T. Ott, F. Sanchez, T. Jiao, et al., Metall. Mater. Trans., 37A, 3251 (2006).
5. A. L. G. Y. Zhang, Appl. Phys. Lett., 89, 071907-1 (2006).
6. O. P. Bobrov, V. A. Khonik, K. Kitagawa, and S. N. Laptev, J. Non-Crystalline Solids, 342,
152 (2004).
7. J. Bonneville, P. Spaig, J.-L. Martin, Proc. M.R.S. Symp., 364, 369 (1995).
8. M. Bletry, P. Guyot, Y. Brechet, et al., Intermetallics, 12, 1051 (2004).
9. W. H. Jiang, F. E. Pinkerton, and M. Atzmon, Scripta Mater., 48, 1195 (2003).
10. T. G. Nieh, T. Mukai, C. T. Liu, and J. Wadsworth, Scripta Mater., 40, 1021 (1999).
Received 28. 06. 2007
170 ISSN 0556-171X. npo6neMbi npouHocmu, 2008, № 1
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