Supplementary
Super elastic strain limit in metallic glass films
Q.K. Jiang1, P. Liu2, †, Y. Ma1, Q. P. Cao1,*, X. D. Wang1, D.X. Zhang3, X. D. Han2,*,
Z. Zhang1,4, J.Z. Jiang1,4*
1
International Center for New-Structured Materials (ICNSM) and Laboratory of
New-Structured Materials, Department of Materials Science and Engineering,
Zhejiang University, Hangzhou 310027, People’s Republic of China
2
Institute of Microstructure and Properties of Advanced Materials, Beijing University
of Technology, Beijing 100124, People’s Republic of China
3
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University,
Hangzhou, 310027, People’s Republic of China
4
State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, 310027,
People’s Republic of China
*Authors to whom correspondence should be addressed: electronic mail:
caoqp@zju.edu.cn，xdhan@bjut.edu.cn, jiangjz@zju.edu.cn
†
Contributes equally with the first author.
PACS numbers: 61.43.Dq, 62.20.F-, 81.05.Kf, 81.40.Lm
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Specimen Preparation Methods and Characterization
Thin films with nominal composition Ni60Nb40 (at.%) with thickness ranging from
50 to 1040 nm were deposited on cleaned Si wafers and Si wafers coated with
photoresist separately in a direct-current magnetron sputtering system (DCMS,
JZCK-400) by controlling the deposition time. The composition of studied films with
various thicknesses was examined by electron dispersive X-ray spectroscopy (EDS)
mounted on field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800)
to be average Ni59.7Nb40.3, which is close to the nominal composition. The thickness,
density and amorphous nature of deposited films were characterized by synchrotron
radiation X-ray reflectivity (SR-XRR) and diffraction (SR-XRD) at beamline
BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF) at a wavelength of
0.12398 nm, field-emission transmission electron microscopy (FE-TEM, JEOL
2100F). A linear relationship between sample thickness and sputtering time is
detected by scanning electron microscopy (SEM) observation in Fig. S1(a), and
further confirmed by SR-XRR technique in Fig. S1(b). Here, sample with thickness
about 50 nm was employed for the in-situ tension tests in TEM.
The preparation of tensile sample is schematically illustrated in Fig. S2. The pulling
force is provided by the bimetallic plates, made of sheets which have different thermal
expansion coefficients (1,2). Upon gradually heating a copper grid (the bimetallic
plates are mounted onto it) in a TEM hot-stage holder with the temperature rise below
100 K, the plates bend. The two plates were arranged to bend slowly in opposite
directions, pulling the specimen at an estimated strain rate of 10-5-10-4 s-1. The
real-time evolution of the sample was captured in situ along with deformation in a
JEOL-2010F FE-TEM. The electron-beam effect on the samples was assumed to be
negligible as the tensile straining was carried out with the electron beam blocked off,
with only intermittent stoppage to expose the sample to the beam for observation,
during which TEM images and diffraction patterns were taken. Throughout the
experiments, the sample holder never reached a temperature above 350 K, as
measured by a thermocouple, which is far below the glass transition temperature of
NiNb metallic glass (about 890 K for bulk metallic glasses). The length evolution was
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determined by measuring the changes in length.
FIG. S1. (A) The film thickness as a function of the deposition time. The insets are
typical SEM images of the fracture surface of the thin films and the film thickness can
be directly measured. (B) XRR data and its best fit for the thinnest film, and from the
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fitting data we can accurately acquire the film thickness about 53±1 nm.
Fig.S2 Schematic illustration for the process of the in situ TEM frame-like sample
preparation by FIB for a magnetron sputtered NiNb metallic glass film. The circled
yellow ring is a 3 mm diameter TEM copper grid, on which two bimetallic plates are
mounted to provide a pulling force at the NiNb metallic glass film samples.
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Fig. S3 The length and elongation evolution for six sample bars (labeled as S3–A,
S3-B, S3-C, S3-D, S3-E, and S3-F, respectively) with points where the bright-field
TEM images were taken.
Fig. S3 exhibits length evolution during in-situ tensile tests in TEM. In all studied
NiNb metallic glass films, lengths have experienced significant uniformly elongation
(about 12~14% strain including elastic and plastic strains) without any obvious shear
banding, necking or crystallization. The unloading data in the Fig. S3 reveals that the
samples undergo only 2-4% permanent plastic deformation strain while about 10%
elastic recoverable elongation occurs for monolithic NiNb metallic glass films, which
is further confirmed by the fracture test in Fig. S4.
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Fig.S4 The evolution of width versus length during tension of as-sputtered sample in
Fig. 5.
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Fig. S5 (A) One-dimensional intensity versus radius of the diffraction ring in the
SAED pattern. (B) Radius change at 0, 10% and 13% tensile strains. It is found that
radius shifts to lower values with the increase in strain. R is determined to be R0=40.6
(as sputtered) and R1= 39.8 (10% tensile strain), with 0.2% uncertainty, respectively.
According to Rd=L at 10% tensile strain, the average atomic distance d variation is
deduced to be about 2.0%, where L is camera length and iswavelength of electron
beam used.
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Fig. S6 Representatively displays the length evolution of relaxed sample bars
labeled as 5-D and 5-F. The samples undergoing 2.5~3.5% strain can completely
recovered and no plastic deformation took place after unloading. When samples
experienced above 5.6% tensile strain, permanent plasticity occurred and followed by
catastrophic fracture. The glass features of these relaxed tensile bars were also
confirmed by the zoomed-in bright-field HRTEM images at different sites together
with diffraction patterns. No crystallization was found, as shown in Fig. S7. These
results confirm that annealing treatment below glass transition temperature lead to the
reduction of elastic strain of glassy NiNb film from about 6.6% for as-sputtered
sample to 3.5% for the relaxed sample, supporting the open-volume mechanism
proposed in this work.
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Fig.S7 Zoomed-in bright-field HRTEM images of the relaxed NiNb glassy bars after
fracture. No crystallization was observed, confirming its amorphous nature.
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