Synthesis and Properties of Carbon Short Fiber Reinforced

ZrCuNiAl Metallic Glass Matrix Composite

Jinmin Liu1;2, Haifeng Zhang1;*, Xiaoguang Yuan2, Huameng Fu1 and Zhuangqi Hu1

1Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences,72 Wenhua Road, Shenyang 110016, P. R. China2School of Materials Science and Engineering, Shenyang University of Technology,111 Shenliao West Road, Shenyang 110870, P. R. China

Carbon short fiber reinforced Zr50:5Cu36:45Ni4:05Al9 metallic glass matrix composite was synthesized. The microstructure, thermalbehavior, and compressive property of composite are investigated. The improvement of thermal stability and Young’s modulus are due to theaddition of short carbon fiber. The limited reaction occurs between the matrix and short fiber by reducing the reactive time, and only a ZrCreaction zone with about 150 nm in width forms. Such interfacial reaction can improve the wettability and tighten the bonding at the interface,and consequently enhance the strength of composite. The effect of interfacial reactive production on the compressive property is alsodiscussed. [doi:10.2320/matertrans.M2010028]

(Received November 17, 2010; Accepted December 9, 2010; Published February 2, 2011)

Keywords: bulk metallic glass, composite, carbon fiber, interface, compressive property

1. Introduction

Monolithic bulk metallic glasses (BMGs) possess unusualmechanical properties compared with conventional crystal-line alloys, such as large elastic limit, high yield strength,and hardness.1,2) And they are favorable matrix materials forcomposites because of their low melting points, low glasstransition temperatures, and strong resistance against heter-ogeneous nucleation.3) Recently synthesizing the compositesby introducing the structural heterogeneity in the metallicglass matrix is a hot topic. It is reported that malleable metalfibers,4) metal particles,5) and refractory ceramics6) havebeen successfully combined with the metallic glass matrix.Carbon fiber metallic glass matrix composites are also paidspecial attention in order to synthesize a promising highstrength and lightweight material. Though the densities ofcarbon long and short fiber composites prepared by meltinfiltration casting are much reduced, the lower compressivefracture strength of them are only under about 1200MPa.7)

The interfacial microstructure analyses revealed that adiffusion zone and a brittle crystalline reaction zone of(Zr+Ti)C form between the metallic glass matrix and fiber,and the max width of zones is up to 900 nm.8) It isspeculated that such excessive interfacial reaction canweaken the interfacial cohesion, hardly transfer the loadingefficiently during compression, and consequently worsen themechanical property.

In this study, we synthesized carbon short fiber reinforcedZr50:5Cu36:45Ni4:05Al9 metallic glass matrix composite bysimilar powder metallurgy method. The improved compres-sive fracture strength and reduced density of carbon shortfiber composite are attained compatibly by reducing theinterfacial reaction. The microstructure of reactive crystallinephase at the interface and its effect on the compressiveproperty are mainly discussed.

2. Experimental

Alloy ingots with a nominal composition of Zr50:5Cu36:45-Ni4:05Al9 were prepared by arc melting the mixtures ofelemental pieces with a purity of 99.5% or better in awater-cooled hearth under Ti-gettered high purity argonatmosphere. Each ingot was re-melted at least four times toensure the chemical homogeneity. Then the ingots werebroken and ground mechanically into fine particle with adiameter of about 250 mm. The polyacrylonitrile (PAN)based amorphous carbon short fibers with a diameter of7 mm and density of 2.2 g cm�3 were cleaned in acetone andethanol, and preheated at 1273K for 1 h under high vacuumbefore mixture. Carbon short fibers with different volumefractions were mixed uniformly with the ingot particles,and dried under vacuum for 2 h. Then the mixtures werecoldly compressed into cylinders with a diameter of 5mm.The cylinders were melted rapidly in a quartz tube byinduction under high purity argon atmosphere, and injectedinto a copper mold to prepare rods of 3mm in diameterand 60–70mm in length. Densities of the composites andundoped BMG were measured by the Archimedes method.The as-cast rods were characterized by X-ray diffractometer(XRD, Cu-K� radiation), transmission electron microscope(TEM) operated at 200 kV with energy-dispersive spec-trometer (EDX), and differential scanning calorimeter(DSC). The TEM samples were obtained by ion thinningwith liquid nitrogen cooling. DSC measurements wereperformed under a continuous argon flow at a heating rateof 0.33K/s. Uniaxial quasistatic compression tests forcylindrical rods with a length/diameter ratio 2 : 1 werecarried out on servo-hydraulic MTS 810 provided with astrain gauge under a constant strain rate of 2� 10�4 s�1 atroom temperature. At least five compressive samples weretested for each alloy to get a statistical result. Fracturemorphology of samples was observed by scanning electronmicroscope (SEM).*Corresponding author, E-mail: hfzhang@imr.ac.cn

Materials Transactions, Vol. 52, No. 3 (2011) pp. 412 to 415#2011 The Japan Institute of Metals

3. Results

Figure 1 shows typical XRD patterns of Zr50:5Cu36:45-Ni4:05Al9 monolithic BMG and composites with 3%, 7% ofcarbon short fiber. XRD patterns of these composites show asuperposition of a broad diffuse diffraction peak character-istic for the amorphous matrix and several small peaksrepresentative for a crystalline phase. The intensities andamounts of crystalline peaks increase with volume fraction offiber increasing. The crystalline peaks are identified as ZrCphase. In addition, no other crystalline phases are detectedwithin the sensitivity limit of XRD.

Figure 2 shows the SEM image of cross-section surfacefor the composite with 7% of carbon short fiber. The fibersare distributed uniformly in the featureless amorphousmatrix. The distribution is mainly due to the processing ofmixing the fibers with the particles of master alloy priorto the casting. The density of Zr50:5Cu36:45Ni4:05Al9 BMGand composites with 3%, 7% of fiber is about 6.7, 6.5, and

6.3 g cm�3 respectively. The results show that the preparedcomposites are fully dense according to the rule-of-mixture.

Thermal behaviors of Zr50:5Cu36:45Ni4:05Al9 BMG andthe composite with 7% of carbon short fiber are shown inFig. 3. They all exhibit an endothermic event, character-istic for glass transition, followed by a clear exothermicevents corresponding to the crystallization reaction. Theglass transition temperature (Tg), the melting temperature(Tm), and the liquid temperature (Tl) of both alloys showno obvious difference. But the crystallization temperature(Tx) of composite clearly shifts to the high temperaturecompared with that of BMG. So the corresponding super-cooled liquid region �T (Tx � Tg) increases, indicating theimprovement of thermal stability. The possible reason isattributed that some carbon atomic with smaller sizerelative to other constituent element can dissolve into thematrix of composite, enhance the amorphous structureand make the rearrangement of the atoms more diffi-cult.9)

Figure 4 shows TEM micrographs of the interfacebetween the metallic glass matrix and carbon short fiber.The matrix and fiber are all no obvious contrast as shown inFig. 4(a). The darker region is the matrix. Its correspondingselected area diffraction (SAD) pattern illustrates twodiffuse rings characteristic for the amorphous structure asshown in the lower-right inset of Fig. 4(a). The lighterregion is a carbon short fiber. The SAD pattern shows asuperposition of turbine shape and amorphous ring, asshown in the upper-left inset of Fig. 4(a). The patterns ofmatrix and fiber show that the primary states of them areretained after processing. It is clear that a reactive zoneforms at the interface between the matrix and carbon shortfiber as shown in Fig. 4(a). The zone in width is about150 nm. It mainly consists of crystalline particles with a sizeof about 100 nm and some small particles. The particleswere further characterized as f.c.c. ZrC phase by SADpattern. The corresponding pattern is shown in Fig. 4(b).The result is also supported by EDX analyses of particles.And no other crystalline phase is detected between the zoneof ZrC and BMG by tilting the sample within a wide degree,

Fig. 1 XRD patterns of Zr50:5Cu36:45Ni4:05Al9 BMG and composites with

3%, 7% of carbon short fiber.

Fig. 2 SEM image of composite with 7% of carbon short fiber.

Fig. 3 DSC curves of Zr50:5Cu36:45Ni4:05Al9 BMG and composite with 7%

of carbon short fiber.

Synthesis and Properties of Carbon Short Fiber Reinforced ZrCuNiAl Metallic Glass Matrix Composite 413

indicating that the interfacial production cannot induce thestructural heterogeneity of BMG.

Figure 5 shows the compressive stress-strain curves ofZr50:5Cu36:45Ni4:05Al9 BMG and composites with 3%, 7% ofcarbon short fiber. They all fail after elastic deformation andalmost no plastic deformation occurs. It is clear that thefracture strength of fiber composite is higher than that ofBMG. The fracture strength of monolithic BMG, compo-sites with 3% and 7% of carbon short fiber is about1923� 10MPa, 2020� 10MPa, and 2182� 10MPa re-spectively. In addition, the Young’s modulus of compositeswith 3% and 7% of carbon short fiber is about 96� 5GPa,104� 5GPa respectively, and they are higher than that ofBMG, 81� 5GPa.

Figure 6 shows the fracture surface of composite with 7%of carbon short fiber. A carbon short fiber is broken alongradial direction, and a portion of carbon short fiber is held onthe fracture surface. One side of the fiber shows vein-likepattern characteristic for typical fracture feature of BMG, andanother side shows smooth region. They suggest that the fibercan hinder the matrix flow to some extent during the finaldeformation event. In addition, the thin amorphous layer withvein-like pattern sticks on the fiber, and the fresh surface offiber exists on the fracture surface. It is deduced that the crackmay occur at the interface.

4. Discussion

It is important to synthesize the composite with desirableproperty by designing and controlling the interfacial reac-tion.10) Some brittle crystalline phases are easily produced byinterfacial reaction because of relative high reactive temper-ature and long time for ex-situ fiber or particle compositesduring the processing. For example, WZr intermetallic format the interface for tungsten wire reinforced Zr-based BMGcomposites.4,11) They can decrease the interfacial bonding,and accordingly hamper the properties. So more effortsare preformed to minimize the reactions in order to strengththe bonding as possibly, such as, optimizing the processparameters, infiltration temperature and time,12) or tailoringthe matrix composition by microalloy method.13) Anotherhand, it is reported that in-situ ZrC particle reinforcedZr55Al10Ni5Cu30 metallic glass matrix composite showshigher fracture strength and larger plastic strain comparedwith ex-situ composite with the same matrix and reinforce-ment. The reason is mainly attributed to the improvement ofinterfacial bonding by use of in-situ reaction.14,15) Theseoperative methods give the clue to prepare carbon short fibercomposite that performing the reasonable processing toreduce the interfacial reaction to attain the better interfacial

Fig. 4 TEM micrographs of interface between metallic glass matrix and carbon short fiber.

Fig. 5 Compressive stress-strain curves of Zr50:5Cu36:45Ni4:05Al9 BMG

and composites with 3%, 7% of carbon short fiber.

Fig. 6 Fracture surface of composite with 7% of carbon short fiber.

414 J. Liu, H. Zhang, X. Yuan, H. Fu and Z. Hu

bonding. Earlier studies show that carbon long or short fibercomposite was prepared by melt infiltration casting withinfiltration temperature, about 1173K, and infiltration time,about 2–15min. It is expected that shortening the reactiontime can reduce the interfacial production. In contrast, thetime is much decreased to about 4–8 second, so only areactive zone of ZrC particle form at the interface, and nodiffuse zone exists for carbon short fiber composite preparedby similar powder metallurgy method in our work. Suchlimited interfacial reaction can contribute to the improvementof strength.16,17) They can improve the wettability andbonding between the matrix and short fiber, ensure the goodloading transfer to the fiber with higher strength and Young’smodulus, and hence enhance the fracture strength andYoung’s modulus of short fiber composite. In addition,carbon short fiber is a stiff reinforcement. So the fibers cannoteffectively hamper the local rapid spread of shear bands(SBs) and induce the seeding of multiple SBs. When theinterfacial cohesion cannot accommodate the loading, thecomposite is ruptured subsequently. Actually the bondingbetween the matrix and reactive crystalline ZrC particle israther stronger than the bonding between ZrC particle andcarbon short fiber. So the mismatch of interfacial bondingmay lead to the fracture earlier occur prior along the interfacebetween ZrC particle and carbon short fiber.

5. Conclusions

In summary, carbon short fiber reinforced Zr50:5Cu36:45-Ni4:05Al9 BMG matrix composite was successfully synthe-sized by similar powder metallurgy method. Carbon shortfibers are well distributed in the matrix. Only a ZrC particlereaction zone with about 150 nm in width forms between thematrix and fiber by reducing the reaction time. The limitedreaction can strengthen the interfacial bonding. The gooddistribution of short fiber and the increase of bonding bothcontribute to improve the compressive fracture strength ofcomposite. The thermal stability and Young’ modulus ofcomposite are increased due to the introduction of carbon

short fiber. These results show that carbon short fiberreinforced Zr-based metallic glass matrix composite is apromising high strength and lightweight materials.

Acknowledgements

The authors gratefully acknowledge the financial supportfrom the National Natural Science Foundation of China(Grant Nos. 50825402, 50731005) and National BasicResearch Program of China (973 Program, Grant No.2011CB606301).

REFERENCES

1) W. L. Johnson: MRS Bull. 24 (1999) 42–56.

2) A. Inoue: Acta Mater. 48 (2000) 279–306.

3) J. Eckert, J. Das, S. Pauly and C. Duhamel: J. Mater. Res. 13 (1998)

2896–2901.

4) R. D. Conner, R. B. Dandliker and W. L. Johnson: Acta Mater. 46

(1998) 6089–6102.

5) H. Choi-Yim, R. D. Conner, F. Szuecs and Johnson: Acta Mater. 50

(2002) 2737–2745.

6) H. Choi-Yim, R. Busch, U. Koster and W. L. Johnson: Acta Mater. 47

(1999) 2455–2462.

7) F. Szuecs, C. P. Kim and W. L. Johnson: Mater. Sci. Forum. 360–362

(2001) 43–48.

8) C. P. Kim, R. Busch, A. Masuhr, H. Choi-Yim and W. L. Johnson:

Appl. Phys. Lett. 79 (2000) 1456–1458.

9) W. H. Wang, Z. Bian, P. Wen, Y. Zhang, M. X. Pan and D. Q. Zhao:

Intermetallics 10 (2002) 1249–1257.

10) J. Eckert, J. Das, S. Pauly and C. Duhamel: J. Mater. Res. 22 (2007)

285–301.

11) N. Liu, G. F. Ma, H. F. Zhang, H. Li, B. Z. Ding, A. M. Wang and Z. Q.

Hu: Mater. Lett. 17–18 (2008) 3195–3197.

12) Z. F. Zhang, J. Eckert and L. Schultz: Acta Mater. 51 (2003) 1167–

1179.

13) M. L.Wang, G. L. Chen, X. Hui, Y. Zhang and Z. Y. Bai: Intermetallics

15 (2007) 1309–1315.

14) H. Kato, T. Hirano, A. Matsuo, Y. Kawamura and A. Inoue: Scr. Mater.

43 (2000) 503–507.

15) H. Kato and A. Inoue: Mater. Trans. 38 (1997) 793–800.

16) M. E. Siegrist and J. F. Loffler: Scr. Mater. 56 (2007) 1079–1082.

17) T. Liu, P. Shen, F. Qiu, Z. F. Yin, Q. L. Lin, Q. C. Jiang and T. Zhang:

Scr. Mater. 60 (2009) 84–87.

Synthesis and Properties of Carbon Short Fiber Reinforced ZrCuNiAl Metallic Glass Matrix Composite 415