�������� �������

High tensile plasticity and strength of a CuZr-based bulk metallic glasscomposite

Zhiliang Ning, Weizhong Liang, Mingxing Zhang, Zongze Li, HaichaoSun, Ailian Liu, Jianfei Sun

PII: S0264-1275(15)30694-8DOI: doi: 10.1016/j.matdes.2015.10.117Reference: JMADE 856

To appear in:

Received date: 7 August 2015Revised date: 17 October 2015Accepted date: 20 October 2015

Please cite this article as: Zhiliang Ning, Weizhong Liang, Mingxing Zhang, Zongze Li,Haichao Sun, Ailian Liu, Jianfei Sun, High tensile plasticity and strength of a CuZr-basedbulk metallic glass composite, (2015), doi: 10.1016/j.matdes.2015.10.117

This is a PDF file of an unedited manuscript that has been accepted for publication.As a service to our customers we are providing this early version of the manuscript.The manuscript will undergo copyediting, typesetting, and review of the resulting proofbefore it is published in its final form. Please note that during the production processerrors may be discovered which could affect the content, and all legal disclaimers thatapply to the journal pertain.

http://dx.doi.org/10.1016/j.matdes.2015.10.117http://dx.doi.org/10.1016/j.matdes.2015.10.117

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

1

High tensile plasticity and strength of a CuZr-based bulk metallic

glass composite

Zhiliang Ning,1*

Weizhong Liang,

2 Mingxing Zhang

3 Zongze Li,

2 Haichao

Sun,1

Ailian Liu2

, Jianfei Sun1

1. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001,

China

2. Heilongjiang University of Science and Technology, Harbin, 150022, China

3. School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD

4072, Australia

* Corresponding author: Tel.: +86-451-88418317; Fax: +86-451-86413904

E-mail address: zhiliangning@sina.com

Abstract： A new approach to improve the tensile ductility of CuZr-based bulk metallic glasses

without significant reduction in high strength is reported. After doping of Nb into CuZr-based

alloy, a composite was formed with a combination of high strength, large tensile plasticity and

strong work-hardening effect. The addition of Nb led to a uniform distribution of single B2-CuZr

phase in the glassy matrix. The optimal tensile properties were attributed to the

deformation-induced martensitic transformation of the B2-CuZr phase, which in turn interacted

with the glassy matrix. In addition, the drastic adiabatic heating on the fracture region also

contributed to the increase in tensile plasticity.

Keywords：Bulk metallic glass; Composite; Martensitic transformation mediated plasticity; Tensile

properties

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

2

1. Introduction

Due to the high strength and hardness, combined with high corrosion resistance, bulk

metallic glasses (BMGs) have strong potential to be used as a new type of structural and

functional materials [1-7]. Currently the bottleneck issues that limit the engineering applications

of BMGs are the room temperature brittleness and strain softening behaviors [8-12]. It has been

considered that development of BMGs composites (BMGCs) that contain either in-situ formed or

externally added crystalline particles within the glassy matrix is an emerging approach to solve

these problems [1-3, 13-17]. A notably tensile ductility resultantly has been achieved in Ti-based

[18-19] and Zr-based [19-21] BMGCs. With increasing the plasticity, the strength of BMGCs is

deteriorated simultaneously. However, the precipitation of the B2-CuZr crystalline phase in the

glassy matrix in a CuZr-based BMGCs has led to concurrent improvement of both tensile plastic

deformation ability and work-hardening capacity [22-24]. The plastic-predeformation-induced

stress state resulted from the B2-CuZr phase in the metallic glass was believed as the reason for

the higher tensile ductility and strain-hardening capability of CuZr BMGCs [25]. However, it is

still unclear how to control the B2-CuZr precipitation, such as the shape and size of the crystalline

particles, and therefore to maximize the advantage of this phase. Up to date, the elucidation of the

correlation between CuZr phase features, and the tensile properties for CuZr-based BMGCs

through controlling compositions is still remained unclearly [24]. Hence, the present work aims to

seek an alternative approach to increase the ductility of a CuZr-based BMGs without significant

reduction in strength through modification of its chemical composition using Nb to partially

replace Cu and to understand the related mechanisms. The selection of Nb as an alloy addition is

based on previous report [27]. That the ductility of BMGCs can be improved by tailoring the

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

3

stacking fault energy. Furthermore, the effects of the chemical composition on the features of the

B2-CuZr crystalline precipitate and then on the tensile properties are also investigated and

discussed.

2. Experimental Procedures

Button ingots of Cu48-xZr48Al4Nbx (x=0, 1, 3, 3.7, 5 at. %) alloys were fabricated by arc

melting of mixtures of the composing element (99.9% purity) in a Ti-gettered argon atmosphere.

All ingots were re-melted four times to ensure chemical homogeneity by applying arc-melting

current of 200 A. Cylindrical rods with 3 mm in diameter and 45 mm long were synthesized by

drop-casting into a copper mould in a purified argon atmosphere. The phase structures were

characterized by X-ray diffraction (XRD) with Cu-Kα radiation (λ=1.5405Å) using a D/MAX-RB

diffractometer and Microarea X-ray diffraction (MAXRD). Microstructures of the cast samples

were examined using a Carl Zeiss optical microscope (OM) and a JEM 2010F field emission

transmission electron microscopy (TEM). Thermal analysis was carried out by a Pyris-1

differential scanning calorimetry (DSC) at a heating rate of 0.33K/s. Tensile tests on the BMGCs

with different Nb content were performed using a dog-bone shape samples in an INSTRON-5569

testing machine with a strain rate of 3.5× 10-4

s-1

. The fracture surfaces of the tensile samples were

observed in a HITACHI S-4700 scanning electron microscope (SEM). In order to investigate the

Young’s modulus and hardness of both the crystals and glassy matrix in the cast samples,

nanoindentation tests were conducted on a TriboIndenter in-situ Nanomechanical test system with

a maximum load of 10 mN.

3. Results and discussion

Fig.1 shows the XRD spectra taken from 3-mm-diameter cylindrical rods of CuZrAl

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

4

BMGCs with various concentrations of Nb doping. Without addition of Nb, both Al2Zr and

B2-CuZr crystalline phases were detected, which is consistent with the previous report [23]. For

the alloy containing 1% Nb, the XRD spectrum shows one broad diffuse peak around the

diffraction angle of 38o without any apparent crystallization peaks, indicating full glassy structure.

The larger mixing degree of CuZrAl ternary system induced by the small amounts addition of Nb

is responsible for the increase of glass-forming ability (GFA). Similar results were reported

previously [28-29]. Further increasing the Nb content from 3% to 5%, an extra peak that

corresponds to the B2-CuZr phase appears on the top of the diffuse peak, suggesting that the

addition of 3-5% Nb promoted the formation of the B2-CuZr phase in the glassy matrix. With

increase in Nb content, the intensity of the B2-CuZr peak increases, indicating higher volume

fraction of the B2-CuZr crystalline phase at higher Nb content. In addition, higher Nb content also

suppressed the formation of the Al2Zr phase as a result of the competitive formation mechanism of

Al3Nb phase during solidification [23, 26]. It is not contradictive that the different amounts of Nb

promote the GFA and the precipitation of B2 CuZr. Minor addition of Nb promotes the GFA due

to increasing mixing degree of CuZrAl system, while the large amount of addition of Nb acts as

the nucleus of B2 CuZr, resulting in the precipitation of B2 CuZr.

To understand the effect of Nb addition on the phase structure evolution of the CuZrAl

BMGCs, DSC analysis was carried out on the Cu48-xZr48Al4Nbx (x=0, 1, 3, 3.7, 5 at.%) alloys

during continuously heating process. The DSC curves that record information of phase

transformations are shown in Fig.2. It can be seen that the transformation in all alloys contains a

glass transition process followed by an exothermic heat characteristic for crystallization. The

ternary Cu48Zr48Al4 alloy without Nb doping exhibits a smaller heat release than that of the alloy

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

5

doped by different Nb contents. The heat released due to the crystallization of these BMGCs

decreases gradually with the increase in Nb concentration from 1% to 5%. This means that the

volume fraction of the amorphous matrix is reduced due to the increase of the volume fraction of

the crystalline phase at higher Nb addition. The volume fractions of the crystalline phase are

estimated to be 8%, 24%, 28% and 40%, for 1%, 3%, 3.7% and 5% Nb-added 3 mm diameter

samples, respectively. This deduced result is consistent with that from XRD analysis. However,

both the glass transition temperature (Tg) and the onset crystallization temperature (Tx), decrease

with increasing Nb concentration. This once again evidences that the addition of Nb promoted the

formation of the B2-CuZr phase in the CuZr-based BMGCs.

Figure.3 presents the optical metallographs of the cross-sectional microstructures of the

Cu48-xZr48Al4Nbx (x=0, 1, 3.7, 5 at. %) alloys. In the Nb-free sample, a larger volume fraction of

the B2-CuZr and Al2Zr phases with various morphologies can be observed in the glassy matrix，as

shown in Fig. 3a. For the alloy with 1% Nb addition (Fig. 3b), only a few small spherical B2-CuZr

particles are found, which agrees with the XRD results. Increasing the Nb content to 3.7%, much

more spherical B2-CuZr particles with a size ranged from ~30 to ~60 μm homogeneously

distributed in the glassy matrix (see Fig. 3c), which likely gives rise to enhanced tensile ductility

because the size of the particles is very close to the plastic zone of the glassy matrix [7]. However,

in the 5% Nb sample, a few B2-CuZr particles with heterogeneous distribution and non-uniform

sizes embedded into the glassy matrix. According to the metallography, it is clear that 3.7% Nb

addition promoted the uniform nucleation of the B2-CuZr particles during the rapid solidification

process. The distribution of B2 CuZr crystals depends on the Nb content, which may be explained

by the nucleation and growth kinetics of the Nb added samples. It is speculated that Nb may act as

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

6

heterogeneous nucleation sites for B2-CuZr phase because the body-centered cubic structure of

Nb (with a lattice parameter of a = 3.3004 Å) is very similar to that of the B2-CuZr phase (a =

3.2562 Å). In addition, the finer B2-CuZr particles in the 3.7%Nb sample is possibly attributed to

the slow growth rate of this particles resulted from the sluggish growth kinetics. Similar effect was

reported for Ta atom in the Cu-Zr-Al alloy, where the growth of B2-CuZr phase was suppressed

by 0.9% Ta addition [5].

The tensile true stress-strain curves of the Cu48-xZr48Al4Nbx (x=0, 1, 3, 3.7, 5 at. %) alloys

are plotted in Fig. 4. The ternary Cu48Zr48Al4 alloy without Nb-doping exhibited typical brittle

fracture with lower fracture strength of 1510 ± 65 MPa without distinct yielding. This implies that

the non-uniformly distributed B2-CuZr and Al2Zr particles in the glassy matrix did not contribute

to both strengthening and enhancement of ductility. 1% to 5% Nb-doping led to increase in the

fracture strength up to 1810 ± 50 MPa at of 3.7% Nb, but only the CuZr-based BMGCs doped by

3.7% Nb exhibited a significantly plastic deformation with the ductility of 7% and a prominent

work-hardening behavior before fracture. 1%, 3% and 5% Nb-added alloys do not show any

significant tensile plasticity, which display the fracture strength of 1700 ± 40, 1782 ± 15 and 1600

± 60 MPa, respectively. It is evident that the larger fracture strength can be achieved in the

CuZr-based BMGCs due to the enhanced glassy forming ability by doping of Nb into CuZr-based

alloy. The addition of 3.7% Nb promoted the martensitic transformation of the reinforcing

B2-CuZr crystals, which was confirmed by the HRTEM image of the 3.7% Nb-added cast sample

shown in Fig.5. Some stacking faults inside the B2 crystals were observed, as indicated by the

white arrow in Fig.5, which is consistent with the features of the B2 crystals in the Co-containing

alloy [10]. These stacking faults greatly promoted the martensitic transformation, thus notably

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

7

improved tensile plasticity of the 3.7% Nb-added alloy.

Previous studies [7, 20] indicated that matching of soft reinforcing particle size to the

characteristic length scale pR can suppress shear band extension and therefore enhances the

plasticity. pR is a materials scale related to fracture toughness in tension, it can be expressed as:

2 2/ 2p IC YR K (1)

where ICK is fracture toughness, and Y is yield strength [20, 24]. For the 3.7% niobium alloy,

pR can be estimated to be 175um by adopting ICK =50MPa m1/2

and Y =1500 MPa. Therefore,

the crystal size of the 3.7% niobium sample matches to the order of magnitude of pR . As a result

the tensile ductility was enhanced.

The fractography of the Cu48-xZr48Al4Nbx (x=0, 3.7, 5at. %) alloys is shown in Fig.6. Fig.6a

exhibits a shear fracture along a shear angle of 35º and a small number of shear bands on the

lateral surface of the Nb-free sample (pointed by the white arrow). In the enlarged area circled by

a white box in Fig. 6a, it can be seen that a spherical B2-CuZr phase inhibits the propagation of

multiple shear bands, as shown in the inset of Fig. 6a. Some dendrites-like patterns and a few

melting drops were observed to appear on the fracture surface of the Nb-free sample, as shown in

Fig. 6b. The shear fracture occurs along a shear angle of 34º for the 5% Nb-added sample, and a

few slender shear bands come out on its lateral surface, as shown in the inset of Fig. 6c. Some

typical round-core patterns appear on the fracture surface with obvious melting character for the

5% Nb-added sample (Fig. 6c). Fig.6d shows that shear fracture occurs along a shear angle of 50º，

larger than 45º，and many short shear bands appear on the lateral surface of the 3.7% Nb-added

sample. The amplificatory image of the area circled by a white box in Fig. 6d shows the distorted

martensite phases with slat structures (see the inset of Fig. 6d), which is the important evidence of

a phase transformation-mediated plasticity. Afterwards, further observations show that some

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

8

vein-like patterns and martensite phases indicated by an oval appear on the fracture surface with a

drastically melting character (Fig.6e). In addition, it is interesting to find a peculiar feature with

the stripped marks near the interface between the martensite particles and the glassy matrix, as

indicated by the black arrow in Fig.6f. The parallel slats of the martensite particles are pointed by

the white arrow in Fig.6f.

For the Cu48-xZr48Al4Nbx (x=0, 3.7, 5 at. %) BMGCs samples, due to the difference in their

microstructures, shear deformation occurs along the different shear angles when subjected to a

tensile load. Their plastic deformation behaviors are mainly controlled by the B2-CuZr phases.

How to understand why the 3.7% Nb-added sample displays a very high tensile plasticity of 7%?

There are martensite phases on the side surface and fracture surface, which implies that the

propagation of the main shear crack may be hindered by the martensite particles in the glassy

matrix. To further confirm this hypothesis, i.e., the tensile deformation-induced martensitic

transformation of the B2-CuZr phase, the Microarea-XRD patterns of the fractured 3.7%

Nb-added sample are obtained and shown in Fig.7. As compared with the XRD pattern taken from

the as-cast 3.7% Nb-added sample, reflection of the B19’ phase appears in different areas on the

tensile fractured surface. Area I and area II are marked in the inset of Fig.7, which correspond to

the beginning position and the concluding position of the shear fracture process.

Moreover, Fig.6f shows that there are some stripped marks on the fracture surface,

suggesting that the martensite particles interacted with the glassy matrix under tensile loading,

similar to the report before [5]. How to further understand clearly the interaction between the

glassy matrix and martensite particles? Nanoindentation tests on the crystallites and glassy matrix

were performed on the Nb-free and 3.7% Nb-added samples, respectively. The load-displacement

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

9

(P-h) curves in load-control mode at different positions of the two samples are shown in Fig.8.

The P-h curves present few displacement discontinuities marks (pointed by arrows) at position

B2-CuZr phase (Fig.8e and 8d), implying the better plastic deformation, and the yielding of the

B2-CuZr phase is suggested to correspond to the initiation of the martensitic transformation [27].

However, at positions glassy matrix and Al2Zr phase, the shape of the P-h curves became

smoother (Fig. 8a, 8b and 8c), indicating of the poorer plastic deformation. The nanoindentation

results are given in Table 1. It is clear that the Young’s modulus and hardness of the microsized

Al2Zr phase in the Nb-free samples are higher than those of the glassy matrix and the B2-CuZr

phase. It can be deduced that the stress would concentrate on the interface between the glassy

matrix and the Al2Zr phase, which leads to the shear fracture of the Nb-free alloy without

plasticity under tension. In addition, the Young’s modulus and hardness of B2-CuZr phase in 3.7%

Nb-added sample are lower than those of the glassy matrix. So, the stress concentrate on the

crystal-glassy matrix interface will be released through the plastic deformation of the B2-CuZr

phase before the yielding of the glassy matrix [5], which eventually leads to the remarkable plastic

deformation of the 3.7% Nb-added alloy.

Accordingly, it is also considered that the deformation-induced martensitic transformation

of the B2-CuZr phase and its interaction with the glassy matrix may lead to the remarkable tensile

ductility in the 3.7% Nb-added sample. Furthermore, the dramatic melting on the fracture region

also contributes to certain tensile plasticity by releasing more elastic energy.

5. Conclusions

Through investigating the microstructures and tensile deformation behaviors of rapid

solidified Cu48-xZr48Al4Nbx (x=0, 1, 3, 3.7, 5 at. %) alloys, the relationship between

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

10

microstructures and mechanical properties at different Nb-doping levels was characterized. The

1-5% Nb additions suppressed precipitation of the Al2Zr phase and induced the formation of single

B2-CuZr phase in the glass matrix, which increased the fracture strength of the Cu48Zr48Al4 alloys.

The BMGCs with uniformly distributed single B2-CuZr phase was obtained in the 3.7% Nb

addition alloy, which exhibited larger tensile ductility and work-hardening capability as well as the

highest fracture strength. The deformation-induced martensitic transformation of the B2-CuZr

phase and the interaction between the glassy matrix and the martensite particle were responsible

for the improved tensile properties. The drastic melting on the fracture region also contributed to

the increase in tensile plasticity. The results highlight that the high strength and large plasticity in

BMGCs could be achieved simultaneously through dominating the interaction between the glassy

matrix and the reinforcing phase tailored by proper alloying.

Acknowledgements

The authors gratefully acknowledge the financial support by the Foundation of Heilongjiang

Province Natural Science (A201103), the Foundation of Heilongjiang Province Education

(12531585), and the National Natural Science of China (51371078) and (51201062).

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

11

References

[1] Wu Y, Wang H, Liu XJ, Chen XH, Hui XD, Zhang Y, et al. Designing bulk metallic glass

composites with enhanced formability and plasticity. J Mater Sci 2014; 30:566-75.

[2] Kuo CN, Huang JC, Du XH, Liu XJ, Nieh TG. Comparison of mechanical response in CuZr-V

and CuZrAl–Co bulk metallic glass composites. J Alloys Compd 2014; 586:14-9.

[3] Song KK, Pauly S, Sun BA, Tan J, Stoica M, Kuhn U, et al. Correlation between the

microstructures and the deformation mechanisms of CuZr-based bulk metallic glass composites.

AIP Adv 2013; 3: 012116.

[4] Huang YJ, Khong JC, Thomas C, Mi J. Understanding the deformation mechanism of

individual phases of a ZrTi-based bulk metallic glass matrix composite using in situ diffraction

and imaging methods. Appl Phys Lett 2014; 104:031912.

[5] Liu ZQ, Li R, Liu G, Su WH, Wang H, Li Y, et al. Microstructural tailoring and improvement

of mechanical properties in CuZr-based bulk metallic glass composites. Acta Mater 2012;

60:3128–39.

[6] Wei R, Yang S, Zhang CJ, He L. Strain rate dependence of mechanical behavior in a

CuZr-based bulk metallic glass composite containing B2-CuZr phase. Mater Sci Eng A 2014;

606:268–75.

[7] Zhang ZY, Wu Y, Zhou J, Song WL, Cao D, Wang H, et al. Effects of Sn addition on phase

formation and mechanical properties of TiCu-based bulk metallic glass composites. Intermetallics

2013; 42:68-76.

[8] Chen G, Zhang XL, Liu CT. High strength and plastic strain of Mg-based bulk metallic glass

composite containing in situ formed intermetallic phases. Scripta Mater 2013; 68:150–3.

[9] Song KK, Pauly S, Sun BA, Zhang Y, Tan J, Kühn U, et al. Formation of Cu-Zr-Al-Er bulk

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

12

metallic glass composites with enhanced deformability. Intermetallics 2012; 30:132–8.

[10] Zhou DQ, Wu Y, Wang H, Hui XD, Liu XJ, Lu ZP. Alloying effects on mechanical properties

of the Cu–Zr–Al bulk metallic glass composites. Comp Mater Sci 2013; 79:187–92.

[11] Gargarella P, Pauly S, Samadi Khoshkhoo M, Kuhn U, Eckert J. Phase formation and

mechanical properties of Ti–Cu–Ni–Zr bulk metallic glass composites. Acta Mater 2014;

65:259–69.

[12] Wu FF, Zhang ZF, Mao SX, Peker A, Eckert J. Effect of annealing on the mechanical

properties and fracture mechanisms of a Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 bulk-metallic-glass

composite. Phys Rev B 2007; 75: 134201.

[13] Choi-Yim H, Busch R, Köster U, Johnson WL. Synthesis and characterization of particulate

reinforced Zr57Nb5Al10Cu15.4Ni12.6 bulk metallic glass composites. Acta Mater 1999; 47: 2455–62.

[14] Zhang W, Ishihara S, Inoue A. Synthesis and mechanical properties of Cu-based Cu-Zr-Ti

bulk glass alloys containing ZrC particles. Mater Trans 2002; 43:1767–70.

[15] Bae DH, Lee MH, Kim DH, Sordelet DJ. Plasticity in Ni59Zr20Ti16Si2Sn3 metallic glass matrix

composites containing brass fibers synthesized by warm extrusion of powders. Appl Phys Lett

2003; 83:2312–4.

[16] Hays CC, Kim CP, Johnson WL. Microstructure controlled shear band pattern formation and

enhanced plasticity of bulk metallic glasses containing in situ formed ductile phase dendrite

dispersions. Phys Rev Lett 2000; 84:2901–4.

[17] Wu FF, Zhang ZF, Peker A, Mao SX, Das J, Eckert J. Strength asymmetry of ductile dendrites

reinforced Zr- and Ti-based composites. J Mater Res 2006; 21:2331–6.

[18] Jeon C, Kim CP, Joo S H, Kim HS, Lee S. High tensile ductility of Ti-based amorphous

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

13

matrix composites modified from conventional Ti–6Al–4V titanium alloy. Acta Mater 2013; 61:

3012–26.

[19] Wu FF, Li ST, Zhang GA, Wu XF, Lin P. Plastic stability of metallic glass composites under

tension. Appl Phys Lett 2013; 103:151910.

[20] Hofmann DC, Suh JY, Wiest A, Demetriou MD, Johnson WL. Designing metallic glass

matrix composites with high toughness and tensile ductility. Nature 2008; 451:1085–9.

[21]Qiao JW, Sun AC, Huang EW, Zhang Y, Liaw PK, Chuang CP. Tensile deformation

micromechanisms for bulk metallic glass matrix composites: from work-hardening to softening.

Acta Mater 2011; 59:4126–37.

[22] Pauly S, Gorantla S, Wang G, Kuhn U, Eckert J. Transformation-mediated ductility in

CuZr-based bulk metallic glasses. Nature Mater 2010; 9:473–7.

[23] Wu Y, Wang H, Wu HH, Zhang ZY, Hui XD, Chen GL, et al. Formation of Cu-Zr-Al bulk

metallic glass composites with improved tensile properties. Acta Mater 2011; 59:2928–36.

[24] Liu ZQ, Liu G, Qu RT, Zhang ZF, Wu SJ, Zhang T. Microstructural percolation assisted

breakthrough of trade-off between strength and ductility in CuZr-based metallic glass composites.

Sci Rep 2014; 4:4167–1–6.

[25] Wu FF, Chan KC, Jiang SS, Chen SH, Wang G. Bulk metallic glass composite with good

tensile ductility, high strength and large elastic strain limit. Sci Rep 2014; 4: 5302–1–6.

[26] Massalski T B. Binary alloy phase diagrams. 2nd ed. Materials Park, Ohio: Asm Intl; 1990.

[27]Wu Y, Zhou DQ, Song WL, Wang H, Zhang ZY, Ma D, et al. Ductilizing bulk metallic glass

composite by tailoring stacking fault energy. Phys Rev Lett 2012; 109:245506.

[28]Wu JL, Pan Y, Li XZ, Wang XF. New insight on glass-forming ability and designing Cu-based

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

14

bulk metallic glasses: the solidification range perspective. Mater Des 2014; 61:199-202.

[29]Zhu JS, Wang YG. Effect of Al addition on the glass forming ability, thermal stability and soft

magnetic properties of (Fe0.83P0.16Cu0.01)100-xAlx nanocrystalline alloys. J Alloys Compd 2015;

652:220-4.

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

15

Figure captions

Fig.1 XRD patterns of the as-cast Cu48-xZr48Al4Nbx alloys with different Nb additions

Fig.2 DSC traces of the as-cast Cu48-xZr48Al4Nbx alloys with different Nb additions

Fig.3 Optical metallographs of the cross-sections microstructures of the as-cast Cu48-xZr48Al4Nbx

alloys with different Nb additions, (a)x=0, (b) x=1, (c) x=3.7, and (d) x=5

Fig.4 Tensile true stress-strain curves of the as-cast Cu48-xZr48Al4Nbx alloys with different Nb

additions

Fig.5 HRTEM image of the B2 nanocrystal embedded in the Cu44.3Zr48Al4Nb3.7 alloy

Fig.6 SEM images of the tensile fracture surface and its lateral surface of the as-cast

Cu48-xZr48Al4Nbx alloys with different Nb additions (a) (b)x=0, (c) x=5, (d) (e)and (f) x=3.7

Fig.7 MAXRD patterns of the 3.7% Nb-added sample fracture surface

Fig.8 Load-displacement curves during Nanoindentation of the Nb-free and 3.7% Nb-added

samples at different positions

20 30 40 50 60 70 80

Al2Zr

CuZrCu48-xZr48Al4Nbx

x=5x=3.7x=3

x=1x=0 Intensity（a.u.） 2θ(deg.)

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

16

Table caption

Tab.1 Young’s modulus E and hardness H obtained from nanoindentation of the Nb-free and 3.7%

Nb-added samples

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

17

Fig.1

20 30 40 50 60 70 80

▲● ▲

●

●

●

●●

●●

Al2Zr ▲

▲ ▲

B2-CuZrCu

48-xZr

48Al

4Nb

x

x=5

x=3.7

x=3

x=1

x=0

Inte

nsi

ty (

a.

u.)

2θ (degree)

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

18

Fig.2

600 700 800

Cu48-x

Zr48

Al4Nb

x

Tx

Tg

x=5

x=3.7

x=3

x=1

x=0

Ex

oth

erm

ic h

eat(

a.u

.)

Temperature(K)

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

19

Fig.3

200um

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

20

Fig.4

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Cu48-x

Zr48

Al4Nb

x

1%

x=5x=3.7x=3x=1x=0

str

ess(M

Pa

)

strain(%)

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

21

Fig.5

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

22

Fig.6

(e)

35o

50o

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

23

Fig.7

20 30 40 50 60 70 80

▲

II

I

▲

●B19

,-CuZr

B2-CuZr

▲

▲

●

●●

●

In

ten

sity

(a.

u.)

2θ (degree)

2.0mm ΙΙ Ι

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

24

Fig.8

2000

4000

6000

8000

10000edcba

a Cu48

Zr48

Al4 Al

2Zr

b Cu44.3

Zr48

Al4Nb

3.7 amorphous

c Cu48

Zr48

Al4 amorphous

d Cu48

Zr48

Al4 B2

e Cu44.3

Zr48

Al4Nb

3.7 B2

Lo

ad

(u

N)

Displacement(nm)

150nm

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

25

Tab.1

Position )(GPaE )(GPaH

Nb0 Nb3.7 Nb0 Nb3.7

B2 80.1±1.6 86.6±4.4 5.04±0.44 3.7±0.4

Al2Zr 92.4±2.6 7.76±0.34

Amorphous 83.4±4 109.0±1.0 6.08±0.28 6.1±0.3

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

26

Graphical abstract

20 30 40 50 60 70 80

▲

II

I

▲

●B19

,-CuZr

B2-CuZr

▲

▲

●

●●

●

Inte

nsi

ty (

a.

u.)

2θ (degree)

2.0mm ΙΙ Ι

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Cu48-x

Zr48

Al4Nb

x

1%

x=5x=3.7x=3x=1x=0

str

ess(M

Pa)

strain(%)

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

27

Highlights

A metallic glass composite was found to exhibit high tensile plasticity and work

hardening

The addition of Nb led to a uniform distribution of B2-CuZr phase in the glassy matrix

The enhanced plasticity was attributed to the martensitic transformation of B2-CuZr

phase

The interaction between martensite particle and glassy matrix further enhanced

plasticity