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Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials
Author’s Accepted Manuscript Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials Song-Jeng Huang, Wei-Yi Peng, Bojana Visic, Alla Zak www.elsevier.com/locate/msea
PII: DOI: Reference:
S0921-5093(17)31358-8 https://doi.org/10.1016/j.msea.2017.10.041 MSA35644
To appear in: Materials Science & Engineering A Received date: 16 August 2017 Revised date: 13 October 2017 Accepted date: 13 October 2017 Cite this article as: Song-Jeng Huang, Wei-Yi Peng, Bojana Visic and Alla Zak, Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials, Materials Science & Engineering A, https://doi.org/10.1016/j.msea.2017.10.041 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 galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Article type: Full Paper
Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials Song-Jeng Huang,a,b*, Wei-Yi Penga, Bojana Visicb, Alla Zakc Prof. S.- J. Huang, W.-Y. Peng a Dept. of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec.4, Keelung Rd., Taipei, 106, Taiwan E-mail: *[email protected], [email protected] Dr. Bojana Visic b Dept. of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 234 Herzl Street, Rehovot 7610001 Israel E-mail: [email protected] Prof. Alla Zak c Holon Institute of Technology, 52 Golomb Street, Holon 5810201, Israel E-mail: [email protected] Abstract In the present work, advanced aluminium metal matrix composite reinforced by nanomaterials is reported. The materials used for the experiments are AA6061 aluminium alloy, compounded with inorganic nanotubes (INT) and fullerene-like (IF) nanoparticles of WS2. Aluminium metal matrix composite with different weight percentage (0.1-0.5wt.%) of the INT and IF were prepared. Both the AA6061 aluminium and the aluminium metal matrix nanocomposites (MMCs) were re-melted by the stirring-casting method. Mechanical properties and microstructure analysis of the nano-MMCs were conducted. The measurements have shown that the hardness, yielding strength, ultimate tensile strength, and ductility were improved by up to 68% compared to the neat alloy for nanoparticles concentrations the range of 0.2 wt%. Metallography microstructure analysis showed that increasing the WS2 INT or IF nanoparticles weight percentage in aluminium metal matrix composite, resulted in a more refined grains. The grain size of the composite matrix was reduced by up to 48.4% compared with that of neat AA6061 alloy ingot. Scanning electron microscope (SEM) analysis showed that addition of 0.5 wt.% of WS2 nanotubes into the Al 1
matrix resulted in INT agglomeration which had deleterious effect on the tensile strength. The composite materials reinforcement mechanism was studied. This analysis showed that the improved mechanical properties of the metal nanocomposites can be predominantly attributed to the differences in thermal expansion coefficients of the WS2 INT (or WS2 IF nanoparticle) and the AA6061 alloy.
Keywords: aluminum metal matrix composite, WS2 nanotube, WS2 fullerene-like nanoparticle, mechanical property.
1. Introduction Aluminium alloy is a kind of light metal that can save energy consumption. Al6061 is one of the most common aluminium alloys for general usage purpose. Al6061 has good mechanical properties and good weldability. Metals reinforced with hard particles are known to exhibit enhanced mechanical properties such as: hardness, Young’s modulus, yield strength and ultimate tensile strength. This reinforcement effect nevertheless comes with a penalty of a reduced ductility, i.e. lower fracture toughness. Hence, many researchers have attempted to fabricate Al-based metal-matrix composites (Al MMCs) utilizing different additives and techniques in order to obtain light-weight Al MMCs with excellent mechanical properties.[1-4] In recent years, ceramic nanoparticles, such as SiC, Al2O3 and others, have been used to reinforce different metallic materials and form
new metal matrix composites. Various
mechanisms for strengthening metal-matrix composites (MMCs) were proposed, including thermal expansion mismatch, Orowan looping, Hall-Petch relation and the shear-lag model. [24]
Due to the high processing temperatures of the MMC, the thermal expansion mismatch
between the nanoparticles and the matrix results in increased dislocation density, increasing thereby the yield strength of the nano-MMCs. The nanoparticles in the matrix can impede dislocation motion during tensile testing. 2
Ezatpour et al.
[1]
fabricated AA6061 /nano Al2O3 composites by stir casting process
through injection of Al2O3 particles into the molten Al alloy along while feeding of Ar gas and using a mechanical stirrer. It was found that for both as-cast and extruded Al MMCs, increasing the amount of Al2O3 nanoparticles up to 1.5 wt%, the yield strength and tensile strength increased but the elongation decreased. Esawi et al. [2] used ball milling to disperse up to 5 wt.% CNT in an Al matrix to form Al MMCs. Improvement of up to 50% in tensile strength and 23% in the stiffness compared to pure aluminium were observed. Inorganic nanotubes (INT) and inorganic fullerene-like (IF) nanoparticles of WS2 possess unique mechanical properties, which make their usage as a composite filler very promising. Tensile tests and buckling experiments of individual WS2 nanotubes were carried out in a high resolution scanning electron microscope by Kaplan-Ashiri et al. [5]. Their studies provided a microscopic picture of the nature of the fracture process, giving insight into the strength; flexibility of the WS2 nanotubes (tensile strength of 16 GPa) and their failure mechanism. Díez-Pascualet et al.
[6]
investigated the thermal and mechanical behaviour of
isotactic polypropylene (iPP) nanocomposites reinforced with different loadings of WS 2 IF nanoparticles. The nanoparticles improved the thermomechanical properties of iPP: raised the glass transition and heat deflection temperatures while decreasing the coefficient of thermal expansion of the polymer nanocomposite. Improvement of the mechanical, thermal, and tribological behavior of different polymers like polyphenylene sulfide (PPS) epoxy
[9]
, poly(ether ether ketone) (PEEK)
[10]
[7]
, Nylon 6
, poly(methyl-methacrylate) (PMMA)
[11]
[8]
,
, etc.
were achieved by adding tiny amounts (0.1-2 wt.%) of INT/ WS2 IF nanoparticles. For example, significant improvement has been recorded in the tribological behaviour of the PEEK/ WS2 IF nanocomposite coatings: their coefficient of friction has been reduced by up to 70% comparing to the neat polymer. In addition, the hardness and modulus of the coating were increased by as much as 60%, and evidence for improved thermal stability were
3
obtained (the temperature of maximum decomposition of the nanocomposite coatings increases by 20–30 °C). The nanocomposites also displayed superior flame retardancy with longer ignition time and reduced peak heat release rate with respect to the neat PEEK. Huang et al.
[12]
fabricated
new Mg MMC nanocomposites, which exhibit much superior mechanical properties vis a vis the pristine alloy. Metallographic investigation demonstrates that the average grain size has been reduced in inverse proportion to the added amounts of nanotubes up to 1 wt%. Physical considerations suggest that the main mechanism responsible for the reinforcement effect lies in the mismatch between the thermal expansion coefficients of the metal and the nanotubes. In the past, metallic and ceramic nanoparticles, as well as CNT were added to aluminium alloys to form Al MMCs with improved mechanical behavior. In the present work, the effect of adding WS2 IF and WS2 INT on the mechanical properties of Al MMCs were investigated. Superior mechanical behaviour was noticed in comparison to the previously studied Al MMCs. 2. Experimental 2.1 Source materials The Al-alloy studied in this work AA6061 was purchased from Taiwan Ta Cheng Aluminium Co. The microstructure of the AA6061 specimen is shown in Figure 1, and its chemical composition as cited by the manufacturer is presented in Table 1. The synthesis of the WS2 INT and WS2 IF as well as their characterization was described in great detail in Reference [13]. They were produced by the solid-gas reaction of slightly reduced WO3 nanoparticles with H2S gas at temperatures between 850-900 °C using a fluidized bed reactor. In average the WS2 INT are 2-10μm and diameter of 70 nm- see Fig. 2. The average diameter of the WS2 IF nanoparticles is 150 nm as shown in Figure 3. 2.2 Fabrication of the MMC nanocomposite 4
The preparation of the present Al MMCs by using the melt-stirring furnace (Figure 4) was described in great details elsewhere
[13-19]
and will therefore be mentioned only very briefly
here. The Al6061 and the WS2 INT (or IF) were placed inside a stainless steel crucible and heated to 250-300°C (the WS2 IF/INT are stable at these temperatures, Ref.
[20]
), in a
resistance-heating furnace for 15 minutes. Then a stirring vane was actuated in the Al MMCs melt; meanwhile, CO2 and SF6 gasses were bubbled into the crucible through the Al MMcs melt to help mixing the melt The CO2 and the SF6 gasses were also helpful in preventing oxidation of the melt by residual water and air. After that, the melt was heated up to 600°C holding for 15 minutes. The crucible was further heated gradually up to 750°C, with the molten alloy being stirred with a rod-like stirrer operated at 350 rev/min for 3 minutes. Finally, the composite melt was poured into a metallic mold. The Al MMCs containing INT with weight fraction of 0.1, 0.2, 0.5 wt% (and IF with weight fraction of 0.1, 0.2 wt%) were now ready for further mechanical testing. Each composition was repeated at least three times. In present preparations, the rod-like stirrer was used both for melting AA6061 and for mixing the nanotubes nanoparticles in the metal melt of Al MMCs. 2.3 Analyses and characterization Optical microscopy was carried out by Zeiss Axiotech 25HD microscope. Micro-Vickers hardness tester associated with VHPro Express software was used for the hardness measurements. Dynamic tensile testing machine MTS was used for the tensile tests according to ASTM E8-69. A high-performance, multi-purpose diffractometer (RIGAKU, Japan) equipped with a rotating Cu anode was used for X-ray diffraction (XRD) analysis. The following electron microscopes were used in this work: SEM model JEOL JSM-6500F, 7426. The SEM was equipped with energy dispersive analysis (EDS) system and Electron backscatter diffraction (EBSD) system.
3. Results and discussion 5
3.1 Metallographic analysis An Al MMCs ingot was cut into 3 sections for metallographic analysis; tensile and hardness tests as indicated in Figure 5. The recipe of the etching solution used for metallography observation is shown in Table 2. Figure 6 show the metallography of AA6061 MMCs with (a) 0.1 wt.% INT, (b) 0.2 wt.% INT, (c) 0.5 wt.% WS2 INT, while Figure 7 shows the results for AA6061 MMCs with (a) 0.1 wt.% and (b) 0.2 wt.% WS2 IF; respectively. It can be observed that the grain size of both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs decreased with increasing INT and IF concentrations. The grain-size analysis is summarized in Figure 8. SEM micrographs of AA6061/ 0.5 wt.% WS2 INT MMCs surface are shown in Figure 910. The nanotubes seem to be well-dispersed in the MMC and they are mostly concentrated in the grain boundaries and defects in the metal crystallite. The grain refinement effect produced by the nanotubes/nanoparticles and their presence in the grain boundaries has a distinctly favorable effect on the mechanical properties of the MMC as shown below. 3.2 Grain refinement The nanoparticles induce crystallites nucleation which impedes the grain-growth. As indicated in Table 3 and Figure 8, the grain size decreases with increasing the concentration of INT or IF in the composite. Al MMCs with 0.1, 0.2 and 0.5 wt.% INT exhibits 13.1, 36.5 and 48.4% reduction in the grain size compared with neat AA6061, respectively. Al MMCs with 0.1and 0.2 wt.% IF has 5.2% and 32.3% grain size reduction compared with the neat AA6061, respectively. From these results it can be concluded that WS2 INT and WS2 IF produce a remarkable reduction in the grain size of AA6061, which favorably affects the mechanical properties of the MMC, as shown below. 3.3 Hardness test The hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs is shown in Figure 11. The hardness of both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs increased with ascending INT and IF concentration. The AA6061/ 0.5 wt.% WS2 INT MMCs exhibits 6
5.1% increase in hardness compared with AA6061. AA6061/ 0.2 wt.% WS2 INT MMCs exhibits 2.1% hardness increase compared to AA6061. However, AA6061 with 0.2 wt.% WS2 IF MMCs showed a meager 1.4 % increase in the hardness. 3.4 Tensile test Figure 12 shows the stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs. The strain-stress curves of the pure Al-alloy and some of the nanocomposites studied in this work, are shown in Fig. 12. The yield strength (YS), ultimate tensile strength (UTS) and elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs as a function of the nanoparticle concentrations are shown in Figure 13-15, respectively. The yield strength, ultimate tensile strength and elongation increased with increasing INT and IF content. However, there exist an optimal content of the added IF/INT, beyond which the mechanical performance is compromised, as shown for Al MMCs with 0.5 wt.% INT. The mechanical properties of AA6061/ 0.5 wt.% WS2 INT MMCs are worse than those of AA6061/ 0.2 wt.% WS2 INT MMCs, due likely to INT agglomeration (Figure 7) and the appearance of macroscopic cracks (Figure 8). These two phenomena are likely to be the main reason for the waning mechanical properties of AA6061/ 0.5 wt.% WS2 INT MMCs. XRD patterns of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs were presented in Figure 16 and 17, respectively. Noticeably, two small reflection peaks from the Al at 38.4xx° and 44.4xx° are shifted with respect to bulk Al#04-0787. This upshift represents a 2-3% contraction in the lattice spacing and is attributed to relaxation of the strain in the Al matrix for both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs. 3.5 Reinforcement mechanisms contribution calculation There are four documented reinforcement mechanisms (Hall-Petch strengthening, coefficient of thermal expansion difference effect, Orowan strengthening and load bearing effect), which are discussed in the literature. In order to elucidate the main mechanism responsible for the reinforcement effect of the IF/INT, the contribution of each mechanism was calculated. The 7
load transfer from the matrix to the nanotube is maintained by the interface. The nanotube can act as a “reinforcement” to carry some of the load. Unfortunately, only nanoparticles with isotropic spherical shape could be used for these calculations. = Δ
=√ β
)…………….…..……(1)
(
b√
………….……(2)
Δ
ln ................................(3) (
Δ
)
…………………….…(4)
The different models and the parameters used for the calculations are presented in great detail in Tables 4 and 5. Some parameters were adapted from references
[21]-[25]
, others were
experimentally determined. The global reiforcment effect can be obtained by summing up the four individual strengthening terms. The calculated contributions of the different mechanisms for the reinforcement of AA6061/ 0.2 wt.% WS2 INT MMCs and AA6061/ 0.2wt.% WS2 IF MMCs are presented in Table 6 and Table 7, respectively. It is clear from the calculations that the greatest contribution for the reinforcement effect is the increase in the dislocations density at the nanotube-Al-alloy matrix due to the large mismatch in the thermal expansion of the two materials. In turn, the dislocations impede the progress of the cracks under load. In contrast to the Hall-Petch mechanism this effect is more local and is limited to the grain boundaries in the vicinity of the nanotube-metal interface. These calculations were not particularly sensitive to the size of the nanoparticles (20-100 nm). However, models taking into account the large anisotropy of the nanotubes would be highly warranted in this case. Further research is required to optimize the process and elucidate the mechanism of the reinforcement effect- in particular using advanced electron microscopy techniques.
8
4. Conclusion Composites of AA6061 MMCs with 0.1, 0.2 and 0.5 wt.% WS2 INT and AA6061 MMCs with 0.1and 0.2 wt.% WS2 IF were fabricated by the stirring-casting method. The Al MMCs reinforced by WS2 INT or WS2 IF exhibit excellent mechanical properties. The significant results can be summarized as follows: 1. Despite the small amounts of WS2 INT their addition led to the remarkable improvements in the mechanical properties of the alloys. Surprisingly, both the tensile strength of the AA6061 alloy MMCs and its elongation were largely improved. 2. Yielding strength, ultimate tensile strength, and ductility of AA6061/ 0.2 wt.% WS2 INT (inorganic nanotubes) MMCs were improved by 15.0%, 20.6% and 67.8%, respectively. 3. Yielding strength, ultimate tensile strength and ductility of AA6061/ 0.2 wt.% WS2 IF (inorganic fullerene-like nanoparticle) MMCs were enhanced by 12.3%, 15.8% and 39.3%, respectively. 4. AA6061/ 0.5 wt.% WS2 INT exhibited the best result in hardness, which were improved by 5.1%. 5. Calculations of the contribution of the different reinforcement mechanisms showed that the differences in thermal expansion coefficients between the WS2 INT or WS2 IF and the AA6061 alloy are the predominant mechanism for improvement of the mechanical properties of the MMC. The thermal mismatch between the nanotubes and the Al-alloy leads to the formation of numerous dislocations in the grain boundaries in the vicinity of the nanotube-matrix interface. These dislocations impede the progress of the cracks under load.
Acknowledgements This research was supported by the Israel Science Foundation and the Israel National NanoInitiative through the FTA program. The authors would like to acknowledge also the support 9
of the Ministry of Science and Technology of Taiwan for supporting this research through a grant (MOST-103-2918-I-011-003).
Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff))
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loading and temperature, Mater. Chem. Phys. 141 (2013) 979-989. M. Naffakh, Ana M. Díez-Pascual, Thermoplastic Polymer Nanocomposites Based on Inorganic Fullerene-like Nanoparticles and Inorganic Nanotubes, J. Phys. Chem. B 113 (2009) 10104-10111. M. Naffakh, C. Marco, M.A. Gomez, I. Jimenez, Novel melt-processable nylon6/inorganic fullerene-like WS2 nanocomposites for critical applications, Mater. Chem. Phys. 129 (2011) 641–648. E. Zohar, S. Baruch, M. Shneider, H. Dodiu, S. Kenig, D.H. Wagner, A. Zak, A. Moshkovith, L. Rapoport, R. Tenne, The Mechanical and Tribological Properties of Epoxy Nanocomposites with WS2 Nanotubes, Sens. Transducers J. 12 (2011) 53–65. X. Hou, C.X. Shan, K.-L. Choy, Microstructures and tribological properties of PEEKbased nanocomposite coatings incorporating inorganic fullerene-like nanoparticles, Surf. & Coating Tech. 202 (2008) 2287-2291. C.S. Reddy, A. Zak, E. Zussman, WS2 nanotubes embedded in PMMA nanofibers as energy absorptive material, J. Mater. Chem. 21 (2011) 16086–16093. S. J. Huang, C. H. Ho, Y. Feldman, R. Tenne, Advanced AZ31 Mg alloy composites reinforced by WS2 nanotubes, J. Alloys Compd. 654 (2016) 15-22.
[13] A. Zak, L. Sallacan-Ecker, A. Margolin, Y. Feldman, R. Popovitz-Biro, A. Albu-Yaron, M. 10
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Genut and R. Tenne, Scaling Up of the WS2 Nanotubes Synthesis, Fullerenes, Nanotubes, Carbon Nanostruct. 19 (2011) 18-26. V.I. Semenov, J.-R. Jeng, S.-J. Huang, L. Sh. Shuster, S.V. Chertovskikh, J.-Zh. Dao, P.-Ch. Lin, S.-J. Hwang, Tribological properties of the AZ91D magnesium alloy hardened with silicon carbide and by severe plastic deformation, J. Fric. Wear. 30 (2009) 194-198. S.-J. Huang, Z.-W. Chen, Grain refinement of AlNp/ AZ91D megnesium metal-matrix composites, Kovove Mater. 49 (2011) 259-264. S.-J. Huang, Y.-R. Jeng, V.I. Semenov, Y.-Z. Dai, Particle Size Effects of Silicon Carbide on Wear Behavior of SiCp-Reinforced Magnesium Matrix Composites, Tribol. Lett. 42 (2011) 7987. M. Besterci, J. Ivan, S.-J. Huang, O. Velgosová, B. Z. Lin, P. Hvizdoš, Damage mechanism of AZ61-F Mg alloy with nano-Al2O3 particles, Kovove Mater. 49 (2011) 451-455. S.-J. Huang, C.-R. Li, K.-L. Yan, Particle Reinforcement of Magnesium Composites SiCp/AZ80 and Their Mechanical Proterties after Heat Treatment, Kovove Mater. 51 (2013) 45-52. Y.-M. Hwang, S.-J. Huang, Y.-S. Huang, Study of seamless tube extrusion of SiCp reinforced AZ61 magnesium alloy composites, Int. J Adv. Manuf Tech., Published online: DOI 10.1007/s00170-013-4927-8, 68 (2013) 1361-1370.
[20] C. Schuffenhauer, G. Wildermuth, J. Felsche, R. Tenne, How stable are inorganic fullerene-like particles? Thermal analysis (STA) of inorganic fullerene-like NbS2, MoS2, and WS2 in oxidizing and inert atmospheres in comparison with the bulk material, Phys. Chem. Chem. Phys. 6 (2004) 3991-4002. DOI: 10.1039/B401048E. [21] P. K. Rohatgi, N. Gupta and S. Alaraj, Thermal Expansion of Aluminum–Fly Ash Cenosphere Composites Synthesized by Pressure Infiltration Technique, J. Compos. Mater. 40 (2006) 1163-1174. [22] Y. Ding, B. Xiao, Thermal Expansion Tensors, Grüneisen Parameters and Phonon Velocities of Bulk MT2 (M= W and Mo; T=S and Se) from First Principles Calculations, RSC Adv, 5 (2015) 18391-18400. [23] N. Ramakrishnan, An analytical study on strengthening of particulate reinforced metal matrix composites, Acta Mater. 44 (1996) 66-77. [24] B. Peng, H. Zhang, H. Shao, Y. Xu, X. Zhang and H. Zhu, Thermal conductivity of monolayer MoS2, MoSe2 and WS2: interplay of mass effect, interatomic bonding and anharmonicity, RSC Adv. 6 (2016) 5767-5773. [25] A. Zak, L. Sallacan-Ecker, A. Margolin, Y. Feldman, R. Popovitz-Biro, A. Albu-Yaron, M. Genut and R. Tenne, Scaling Up of the WS2 Nanotubes Synthesis, Fullerenes, Nanotubes, Carbon Nanostruct. 19 (2011) 18-26.
11
Table List: Table 1. Chemical composition (in wt%) of the AA6061 alloy Table 2. Recipe of the etching solution used for the preparation of the metallographic specimen Table 3. Grain size of the MMCs with different additives Table 4. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 INT MMCs Table 5. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 IF MMCs Table 6. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 INT MMCs Table 7. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 IF MMCs
12
Figure List: Figure 1. SEM image of AA6061aluminium alloy Figure 2. SEM picture of tungsten disulfide nanotubes (WS2 INT) Figure 3. SEM image of fullerene-like tungsten disulfide (WS2 IF) nanoparticles Figure 4. Schematic rendering of the reactor used for the fabrication of the Al MMCs Figure 5. Ingot sections for metallographic, tensile and hardness tests Figure 6. Metallography of AA6061 MMCs with added (a) 0.1, (b) 0.2 and (c) 0.5 wt.% WS2 INT Figure 7. Metallography of AA6061 MMCs with (a) 0.1 and (b) 0.2 wt.% WS2 IF Figure 8. Grain size analysis of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 9. INT decorating a defect in AA6061/ 0.5 wt.% WS2 INT MMCs Figure 10. Defect of AA6061/ 0.5 wt.% WS2 INT MMCs Figure 11. Hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 12. Stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 13. Yield strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 14. Ultimate tensile strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 15. Elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 16. XRD patterns of AA6061/ WS2 INT MMCs Figure 17. XRD patterns of AA6061/ WS2 IF MMCs
13
Si 0.70
Fe 0.09
Table 1. Chemical composition (in wt%) of the AA6061 alloy Cu Mn Mg Cr Zn Ti Al 0.27 0.004 0.90 0.10 0.01 0.008 Bal.
Table 2. Recipe of the etching solution used for the preparation of the metallographic specimen Recipe of etching NaOH (g) Deionized water (ml) Etching time (sec) 5 95 150 Table 3. Grain size of the MMCs with different additives wt.% of INT or IF Grain size (μm) AA6061 0 105.5 0.1 91.6 AA6061/ WS2 INT 0.2 66.9 MMCs 0.5 54.4 0.1 100.0 AA6061/ WS2 IF MMCs 0.2 71.4
Table 4. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 INT MMCs Parameter
Description coefficient of thermal expansion of the matrix coefficient of thermal expansion of the nanoparticles dislocation strengthening coefficient magnitude of the burgers vector average grain size in the composite sample average grain size in the monolithic sample
Value
Reference/note
22 x 10-6℃-1
[21]
15.9 x 10-6℃-1
[22]
1.25 0.286nm
[23] [24]
66.9μm
experimentally determined
105.5μm
experimentally determined
dp
nanotube diameter
70nm
Gm
shear modulus of the matrix
26GPa
Ky
Hall-Petch material constant
0.062MPa√
Tprocess Ttest
processing temperature testing temperature
750℃ 25℃
Vp
volume fraction of nanoparticles
0.00072
σym
yield stress of the matrix
122MPa
αm αp β b dc dm
14
manufacture supplied average nanotube size calculation and experimentally determined calculation and experimentally determined calculated from weight fraction experimentally determined
Table 5. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 IF MMCs Parameter
Description coefficient of thermal expansion of the matrix coefficient of thermal expansion of the nanoparticles dislocation strengthening coefficient magnitude of the burgers vector average grain size in the composite sample average grain size in the monolithic sample
Value
Reference/note
22 x 10-6℃-1
[21]
14.8 x 10-6℃-1
[25]
1.25 0.286nm
[23] [24]
71.4μm
experimentally determined
105.5μm
experimentally determined
dp
fullerene-like diameter
150nm
Gm
shear modulus of the matrix
26GPa
Ky
Hall-Petch material constant
0.062MPa√
Tprocess Ttest
processing temperature testing temperature
750℃ 25℃
Vp
volume fraction of nanoparticles
0.00072
σym
yield stress of the matrix
119MPa
αm αp β b dc dm
calculation and experimentally determined calculation and experimentally determined calculation and experimentally determined calculated from weight fraction experimentally determined
Table 6. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 INT MMCs Percentage of Symbol Description Value (MPa) strengthening contribution enhancement of composite strength 1.54 4.8% due to grain refining enhancement of composite strength 22.25 68.9% Δ due to dislocation density increase enhancement of composite strength 8.45 26.2% Δ due to Orowan strengthening enhancement of composite strength 0.04 0.1% Δ due to load bearing
Table 7. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 IF MMCs Percentage of Symbol Description Value (MPa) strengthening contribution enhancement of composite strength 1.30 5.8% due to grain refining enhancement of composite strength 16.51 73.6% Δ 15
Δ Δ
due to dislocation density increase enhancement of composite strength due to Orowan strengthening enhancement of composite strength due to load bearing
4.57
20.3%
0.04
0.2%
Figure 1. SEM image of AA6061aluminium alloy
Figure 2. SEM picture of tungsten disulfide nanotubes (WS2 INT)
16
Figure 3. SEM image of fullerene-like tungsten disulfide (WS2 IF) nanoparticles
Figure 4. Schematic rendering of the reactor used for the fabrication of the Al MMCs
17
Figure 5. Ingot sections for metallographic, tensile and hardness tests
AA6061-0 wt.% WS2 INT /100x
AA6061-0 wt.% WS2 INT /200x
AA6061-0.1 wt.% WS2 INT /100x
AA6061-0.1 wt.% WS2 INT /200x
18
AA6061-0.2 wt.% WS2 INT /100x
AA6061-0.2 wt.% WS2 INT /200x
AA6061-0.5 wt.% WS2 INT /100x
AA6061-0.5 wt.% WS2 INT /200x
Figure 6. Metallography of AA6061 MMCs with added (a) 0.1, (b) 0.2 and (c) 0.5 wt.% WS2 INT
AA6061-0.1 wt.% WS2 IF /100x
AA6061-0.1 wt.% WS2 IF /200x
19
AA6061-0.2 wt.% WS2 IF /100x
AA6061-0.2 wt.% WS2 IF /200x
Figure 7. Metallography of AA6061 MMCs with (a) 0.1 and (b) 0.2 wt.% WS2 IF
Figure 8. Grain size analysis of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
Figure 9. INT decorating a defect in AA6061/ 0.5 wt.% WS2 INT MMCs 20
Figure 10. Defect of AA6061/ 0.5 wt.% WS2 INT MMCs
Figure 11. Hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
21
Figure 12. Stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
Figure 13. Yield strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
22
Figure 14. Ultimate tensile strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
Figure 15. Elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
23
Figure 16. XRD patterns of AA6061/ WS2 INT MMCs
24
Figure 17. XRD patterns of AA6061/ WS2 IF MMCs
25
PII: DOI: Reference:
S0921-5093(17)31358-8 https://doi.org/10.1016/j.msea.2017.10.041 MSA35644
To appear in: Materials Science & Engineering A Received date: 16 August 2017 Revised date: 13 October 2017 Accepted date: 13 October 2017 Cite this article as: Song-Jeng Huang, Wei-Yi Peng, Bojana Visic and Alla Zak, Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials, Materials Science & Engineering A, https://doi.org/10.1016/j.msea.2017.10.041 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 galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Article type: Full Paper
Al alloy metal matrix composites reinforced by WS2 inorganic nanomaterials Song-Jeng Huang,a,b*, Wei-Yi Penga, Bojana Visicb, Alla Zakc Prof. S.- J. Huang, W.-Y. Peng a Dept. of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec.4, Keelung Rd., Taipei, 106, Taiwan E-mail: *[email protected], [email protected] Dr. Bojana Visic b Dept. of Materials and Interfaces, Faculty of Chemistry, Weizmann Institute of Science, 234 Herzl Street, Rehovot 7610001 Israel E-mail: [email protected] Prof. Alla Zak c Holon Institute of Technology, 52 Golomb Street, Holon 5810201, Israel E-mail: [email protected] Abstract In the present work, advanced aluminium metal matrix composite reinforced by nanomaterials is reported. The materials used for the experiments are AA6061 aluminium alloy, compounded with inorganic nanotubes (INT) and fullerene-like (IF) nanoparticles of WS2. Aluminium metal matrix composite with different weight percentage (0.1-0.5wt.%) of the INT and IF were prepared. Both the AA6061 aluminium and the aluminium metal matrix nanocomposites (MMCs) were re-melted by the stirring-casting method. Mechanical properties and microstructure analysis of the nano-MMCs were conducted. The measurements have shown that the hardness, yielding strength, ultimate tensile strength, and ductility were improved by up to 68% compared to the neat alloy for nanoparticles concentrations the range of 0.2 wt%. Metallography microstructure analysis showed that increasing the WS2 INT or IF nanoparticles weight percentage in aluminium metal matrix composite, resulted in a more refined grains. The grain size of the composite matrix was reduced by up to 48.4% compared with that of neat AA6061 alloy ingot. Scanning electron microscope (SEM) analysis showed that addition of 0.5 wt.% of WS2 nanotubes into the Al 1
matrix resulted in INT agglomeration which had deleterious effect on the tensile strength. The composite materials reinforcement mechanism was studied. This analysis showed that the improved mechanical properties of the metal nanocomposites can be predominantly attributed to the differences in thermal expansion coefficients of the WS2 INT (or WS2 IF nanoparticle) and the AA6061 alloy.
Keywords: aluminum metal matrix composite, WS2 nanotube, WS2 fullerene-like nanoparticle, mechanical property.
1. Introduction Aluminium alloy is a kind of light metal that can save energy consumption. Al6061 is one of the most common aluminium alloys for general usage purpose. Al6061 has good mechanical properties and good weldability. Metals reinforced with hard particles are known to exhibit enhanced mechanical properties such as: hardness, Young’s modulus, yield strength and ultimate tensile strength. This reinforcement effect nevertheless comes with a penalty of a reduced ductility, i.e. lower fracture toughness. Hence, many researchers have attempted to fabricate Al-based metal-matrix composites (Al MMCs) utilizing different additives and techniques in order to obtain light-weight Al MMCs with excellent mechanical properties.[1-4] In recent years, ceramic nanoparticles, such as SiC, Al2O3 and others, have been used to reinforce different metallic materials and form
new metal matrix composites. Various
mechanisms for strengthening metal-matrix composites (MMCs) were proposed, including thermal expansion mismatch, Orowan looping, Hall-Petch relation and the shear-lag model. [24]
Due to the high processing temperatures of the MMC, the thermal expansion mismatch
between the nanoparticles and the matrix results in increased dislocation density, increasing thereby the yield strength of the nano-MMCs. The nanoparticles in the matrix can impede dislocation motion during tensile testing. 2
Ezatpour et al.
[1]
fabricated AA6061 /nano Al2O3 composites by stir casting process
through injection of Al2O3 particles into the molten Al alloy along while feeding of Ar gas and using a mechanical stirrer. It was found that for both as-cast and extruded Al MMCs, increasing the amount of Al2O3 nanoparticles up to 1.5 wt%, the yield strength and tensile strength increased but the elongation decreased. Esawi et al. [2] used ball milling to disperse up to 5 wt.% CNT in an Al matrix to form Al MMCs. Improvement of up to 50% in tensile strength and 23% in the stiffness compared to pure aluminium were observed. Inorganic nanotubes (INT) and inorganic fullerene-like (IF) nanoparticles of WS2 possess unique mechanical properties, which make their usage as a composite filler very promising. Tensile tests and buckling experiments of individual WS2 nanotubes were carried out in a high resolution scanning electron microscope by Kaplan-Ashiri et al. [5]. Their studies provided a microscopic picture of the nature of the fracture process, giving insight into the strength; flexibility of the WS2 nanotubes (tensile strength of 16 GPa) and their failure mechanism. Díez-Pascualet et al.
[6]
investigated the thermal and mechanical behaviour of
isotactic polypropylene (iPP) nanocomposites reinforced with different loadings of WS 2 IF nanoparticles. The nanoparticles improved the thermomechanical properties of iPP: raised the glass transition and heat deflection temperatures while decreasing the coefficient of thermal expansion of the polymer nanocomposite. Improvement of the mechanical, thermal, and tribological behavior of different polymers like polyphenylene sulfide (PPS) epoxy
[9]
, poly(ether ether ketone) (PEEK)
[10]
[7]
, Nylon 6
, poly(methyl-methacrylate) (PMMA)
[11]
[8]
,
, etc.
were achieved by adding tiny amounts (0.1-2 wt.%) of INT/ WS2 IF nanoparticles. For example, significant improvement has been recorded in the tribological behaviour of the PEEK/ WS2 IF nanocomposite coatings: their coefficient of friction has been reduced by up to 70% comparing to the neat polymer. In addition, the hardness and modulus of the coating were increased by as much as 60%, and evidence for improved thermal stability were
3
obtained (the temperature of maximum decomposition of the nanocomposite coatings increases by 20–30 °C). The nanocomposites also displayed superior flame retardancy with longer ignition time and reduced peak heat release rate with respect to the neat PEEK. Huang et al.
[12]
fabricated
new Mg MMC nanocomposites, which exhibit much superior mechanical properties vis a vis the pristine alloy. Metallographic investigation demonstrates that the average grain size has been reduced in inverse proportion to the added amounts of nanotubes up to 1 wt%. Physical considerations suggest that the main mechanism responsible for the reinforcement effect lies in the mismatch between the thermal expansion coefficients of the metal and the nanotubes. In the past, metallic and ceramic nanoparticles, as well as CNT were added to aluminium alloys to form Al MMCs with improved mechanical behavior. In the present work, the effect of adding WS2 IF and WS2 INT on the mechanical properties of Al MMCs were investigated. Superior mechanical behaviour was noticed in comparison to the previously studied Al MMCs. 2. Experimental 2.1 Source materials The Al-alloy studied in this work AA6061 was purchased from Taiwan Ta Cheng Aluminium Co. The microstructure of the AA6061 specimen is shown in Figure 1, and its chemical composition as cited by the manufacturer is presented in Table 1. The synthesis of the WS2 INT and WS2 IF as well as their characterization was described in great detail in Reference [13]. They were produced by the solid-gas reaction of slightly reduced WO3 nanoparticles with H2S gas at temperatures between 850-900 °C using a fluidized bed reactor. In average the WS2 INT are 2-10μm and diameter of 70 nm- see Fig. 2. The average diameter of the WS2 IF nanoparticles is 150 nm as shown in Figure 3. 2.2 Fabrication of the MMC nanocomposite 4
The preparation of the present Al MMCs by using the melt-stirring furnace (Figure 4) was described in great details elsewhere
[13-19]
and will therefore be mentioned only very briefly
here. The Al6061 and the WS2 INT (or IF) were placed inside a stainless steel crucible and heated to 250-300°C (the WS2 IF/INT are stable at these temperatures, Ref.
[20]
), in a
resistance-heating furnace for 15 minutes. Then a stirring vane was actuated in the Al MMCs melt; meanwhile, CO2 and SF6 gasses were bubbled into the crucible through the Al MMcs melt to help mixing the melt The CO2 and the SF6 gasses were also helpful in preventing oxidation of the melt by residual water and air. After that, the melt was heated up to 600°C holding for 15 minutes. The crucible was further heated gradually up to 750°C, with the molten alloy being stirred with a rod-like stirrer operated at 350 rev/min for 3 minutes. Finally, the composite melt was poured into a metallic mold. The Al MMCs containing INT with weight fraction of 0.1, 0.2, 0.5 wt% (and IF with weight fraction of 0.1, 0.2 wt%) were now ready for further mechanical testing. Each composition was repeated at least three times. In present preparations, the rod-like stirrer was used both for melting AA6061 and for mixing the nanotubes nanoparticles in the metal melt of Al MMCs. 2.3 Analyses and characterization Optical microscopy was carried out by Zeiss Axiotech 25HD microscope. Micro-Vickers hardness tester associated with VHPro Express software was used for the hardness measurements. Dynamic tensile testing machine MTS was used for the tensile tests according to ASTM E8-69. A high-performance, multi-purpose diffractometer (RIGAKU, Japan) equipped with a rotating Cu anode was used for X-ray diffraction (XRD) analysis. The following electron microscopes were used in this work: SEM model JEOL JSM-6500F, 7426. The SEM was equipped with energy dispersive analysis (EDS) system and Electron backscatter diffraction (EBSD) system.
3. Results and discussion 5
3.1 Metallographic analysis An Al MMCs ingot was cut into 3 sections for metallographic analysis; tensile and hardness tests as indicated in Figure 5. The recipe of the etching solution used for metallography observation is shown in Table 2. Figure 6 show the metallography of AA6061 MMCs with (a) 0.1 wt.% INT, (b) 0.2 wt.% INT, (c) 0.5 wt.% WS2 INT, while Figure 7 shows the results for AA6061 MMCs with (a) 0.1 wt.% and (b) 0.2 wt.% WS2 IF; respectively. It can be observed that the grain size of both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs decreased with increasing INT and IF concentrations. The grain-size analysis is summarized in Figure 8. SEM micrographs of AA6061/ 0.5 wt.% WS2 INT MMCs surface are shown in Figure 910. The nanotubes seem to be well-dispersed in the MMC and they are mostly concentrated in the grain boundaries and defects in the metal crystallite. The grain refinement effect produced by the nanotubes/nanoparticles and their presence in the grain boundaries has a distinctly favorable effect on the mechanical properties of the MMC as shown below. 3.2 Grain refinement The nanoparticles induce crystallites nucleation which impedes the grain-growth. As indicated in Table 3 and Figure 8, the grain size decreases with increasing the concentration of INT or IF in the composite. Al MMCs with 0.1, 0.2 and 0.5 wt.% INT exhibits 13.1, 36.5 and 48.4% reduction in the grain size compared with neat AA6061, respectively. Al MMCs with 0.1and 0.2 wt.% IF has 5.2% and 32.3% grain size reduction compared with the neat AA6061, respectively. From these results it can be concluded that WS2 INT and WS2 IF produce a remarkable reduction in the grain size of AA6061, which favorably affects the mechanical properties of the MMC, as shown below. 3.3 Hardness test The hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs is shown in Figure 11. The hardness of both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs increased with ascending INT and IF concentration. The AA6061/ 0.5 wt.% WS2 INT MMCs exhibits 6
5.1% increase in hardness compared with AA6061. AA6061/ 0.2 wt.% WS2 INT MMCs exhibits 2.1% hardness increase compared to AA6061. However, AA6061 with 0.2 wt.% WS2 IF MMCs showed a meager 1.4 % increase in the hardness. 3.4 Tensile test Figure 12 shows the stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs. The strain-stress curves of the pure Al-alloy and some of the nanocomposites studied in this work, are shown in Fig. 12. The yield strength (YS), ultimate tensile strength (UTS) and elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs as a function of the nanoparticle concentrations are shown in Figure 13-15, respectively. The yield strength, ultimate tensile strength and elongation increased with increasing INT and IF content. However, there exist an optimal content of the added IF/INT, beyond which the mechanical performance is compromised, as shown for Al MMCs with 0.5 wt.% INT. The mechanical properties of AA6061/ 0.5 wt.% WS2 INT MMCs are worse than those of AA6061/ 0.2 wt.% WS2 INT MMCs, due likely to INT agglomeration (Figure 7) and the appearance of macroscopic cracks (Figure 8). These two phenomena are likely to be the main reason for the waning mechanical properties of AA6061/ 0.5 wt.% WS2 INT MMCs. XRD patterns of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs were presented in Figure 16 and 17, respectively. Noticeably, two small reflection peaks from the Al at 38.4xx° and 44.4xx° are shifted with respect to bulk Al#04-0787. This upshift represents a 2-3% contraction in the lattice spacing and is attributed to relaxation of the strain in the Al matrix for both AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs. 3.5 Reinforcement mechanisms contribution calculation There are four documented reinforcement mechanisms (Hall-Petch strengthening, coefficient of thermal expansion difference effect, Orowan strengthening and load bearing effect), which are discussed in the literature. In order to elucidate the main mechanism responsible for the reinforcement effect of the IF/INT, the contribution of each mechanism was calculated. The 7
load transfer from the matrix to the nanotube is maintained by the interface. The nanotube can act as a “reinforcement” to carry some of the load. Unfortunately, only nanoparticles with isotropic spherical shape could be used for these calculations. = Δ
=√ β
)…………….…..……(1)
(
b√
………….……(2)
Δ
ln ................................(3) (
Δ
)
…………………….…(4)
The different models and the parameters used for the calculations are presented in great detail in Tables 4 and 5. Some parameters were adapted from references
[21]-[25]
, others were
experimentally determined. The global reiforcment effect can be obtained by summing up the four individual strengthening terms. The calculated contributions of the different mechanisms for the reinforcement of AA6061/ 0.2 wt.% WS2 INT MMCs and AA6061/ 0.2wt.% WS2 IF MMCs are presented in Table 6 and Table 7, respectively. It is clear from the calculations that the greatest contribution for the reinforcement effect is the increase in the dislocations density at the nanotube-Al-alloy matrix due to the large mismatch in the thermal expansion of the two materials. In turn, the dislocations impede the progress of the cracks under load. In contrast to the Hall-Petch mechanism this effect is more local and is limited to the grain boundaries in the vicinity of the nanotube-metal interface. These calculations were not particularly sensitive to the size of the nanoparticles (20-100 nm). However, models taking into account the large anisotropy of the nanotubes would be highly warranted in this case. Further research is required to optimize the process and elucidate the mechanism of the reinforcement effect- in particular using advanced electron microscopy techniques.
8
4. Conclusion Composites of AA6061 MMCs with 0.1, 0.2 and 0.5 wt.% WS2 INT and AA6061 MMCs with 0.1and 0.2 wt.% WS2 IF were fabricated by the stirring-casting method. The Al MMCs reinforced by WS2 INT or WS2 IF exhibit excellent mechanical properties. The significant results can be summarized as follows: 1. Despite the small amounts of WS2 INT their addition led to the remarkable improvements in the mechanical properties of the alloys. Surprisingly, both the tensile strength of the AA6061 alloy MMCs and its elongation were largely improved. 2. Yielding strength, ultimate tensile strength, and ductility of AA6061/ 0.2 wt.% WS2 INT (inorganic nanotubes) MMCs were improved by 15.0%, 20.6% and 67.8%, respectively. 3. Yielding strength, ultimate tensile strength and ductility of AA6061/ 0.2 wt.% WS2 IF (inorganic fullerene-like nanoparticle) MMCs were enhanced by 12.3%, 15.8% and 39.3%, respectively. 4. AA6061/ 0.5 wt.% WS2 INT exhibited the best result in hardness, which were improved by 5.1%. 5. Calculations of the contribution of the different reinforcement mechanisms showed that the differences in thermal expansion coefficients between the WS2 INT or WS2 IF and the AA6061 alloy are the predominant mechanism for improvement of the mechanical properties of the MMC. The thermal mismatch between the nanotubes and the Al-alloy leads to the formation of numerous dislocations in the grain boundaries in the vicinity of the nanotube-matrix interface. These dislocations impede the progress of the cracks under load.
Acknowledgements This research was supported by the Israel Science Foundation and the Israel National NanoInitiative through the FTA program. The authors would like to acknowledge also the support 9
of the Ministry of Science and Technology of Taiwan for supporting this research through a grant (MOST-103-2918-I-011-003).
Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff))
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[8]
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loading and temperature, Mater. Chem. Phys. 141 (2013) 979-989. M. Naffakh, Ana M. Díez-Pascual, Thermoplastic Polymer Nanocomposites Based on Inorganic Fullerene-like Nanoparticles and Inorganic Nanotubes, J. Phys. Chem. B 113 (2009) 10104-10111. M. Naffakh, C. Marco, M.A. Gomez, I. Jimenez, Novel melt-processable nylon6/inorganic fullerene-like WS2 nanocomposites for critical applications, Mater. Chem. Phys. 129 (2011) 641–648. E. Zohar, S. Baruch, M. Shneider, H. Dodiu, S. Kenig, D.H. Wagner, A. Zak, A. Moshkovith, L. Rapoport, R. Tenne, The Mechanical and Tribological Properties of Epoxy Nanocomposites with WS2 Nanotubes, Sens. Transducers J. 12 (2011) 53–65. X. Hou, C.X. Shan, K.-L. Choy, Microstructures and tribological properties of PEEKbased nanocomposite coatings incorporating inorganic fullerene-like nanoparticles, Surf. & Coating Tech. 202 (2008) 2287-2291. C.S. Reddy, A. Zak, E. Zussman, WS2 nanotubes embedded in PMMA nanofibers as energy absorptive material, J. Mater. Chem. 21 (2011) 16086–16093. S. J. Huang, C. H. Ho, Y. Feldman, R. Tenne, Advanced AZ31 Mg alloy composites reinforced by WS2 nanotubes, J. Alloys Compd. 654 (2016) 15-22.
[13] A. Zak, L. Sallacan-Ecker, A. Margolin, Y. Feldman, R. Popovitz-Biro, A. Albu-Yaron, M. 10
[14] [15] [16] [17] [18] [19]
Genut and R. Tenne, Scaling Up of the WS2 Nanotubes Synthesis, Fullerenes, Nanotubes, Carbon Nanostruct. 19 (2011) 18-26. V.I. Semenov, J.-R. Jeng, S.-J. Huang, L. Sh. Shuster, S.V. Chertovskikh, J.-Zh. Dao, P.-Ch. Lin, S.-J. Hwang, Tribological properties of the AZ91D magnesium alloy hardened with silicon carbide and by severe plastic deformation, J. Fric. Wear. 30 (2009) 194-198. S.-J. Huang, Z.-W. Chen, Grain refinement of AlNp/ AZ91D megnesium metal-matrix composites, Kovove Mater. 49 (2011) 259-264. S.-J. Huang, Y.-R. Jeng, V.I. Semenov, Y.-Z. Dai, Particle Size Effects of Silicon Carbide on Wear Behavior of SiCp-Reinforced Magnesium Matrix Composites, Tribol. Lett. 42 (2011) 7987. M. Besterci, J. Ivan, S.-J. Huang, O. Velgosová, B. Z. Lin, P. Hvizdoš, Damage mechanism of AZ61-F Mg alloy with nano-Al2O3 particles, Kovove Mater. 49 (2011) 451-455. S.-J. Huang, C.-R. Li, K.-L. Yan, Particle Reinforcement of Magnesium Composites SiCp/AZ80 and Their Mechanical Proterties after Heat Treatment, Kovove Mater. 51 (2013) 45-52. Y.-M. Hwang, S.-J. Huang, Y.-S. Huang, Study of seamless tube extrusion of SiCp reinforced AZ61 magnesium alloy composites, Int. J Adv. Manuf Tech., Published online: DOI 10.1007/s00170-013-4927-8, 68 (2013) 1361-1370.
[20] C. Schuffenhauer, G. Wildermuth, J. Felsche, R. Tenne, How stable are inorganic fullerene-like particles? Thermal analysis (STA) of inorganic fullerene-like NbS2, MoS2, and WS2 in oxidizing and inert atmospheres in comparison with the bulk material, Phys. Chem. Chem. Phys. 6 (2004) 3991-4002. DOI: 10.1039/B401048E. [21] P. K. Rohatgi, N. Gupta and S. Alaraj, Thermal Expansion of Aluminum–Fly Ash Cenosphere Composites Synthesized by Pressure Infiltration Technique, J. Compos. Mater. 40 (2006) 1163-1174. [22] Y. Ding, B. Xiao, Thermal Expansion Tensors, Grüneisen Parameters and Phonon Velocities of Bulk MT2 (M= W and Mo; T=S and Se) from First Principles Calculations, RSC Adv, 5 (2015) 18391-18400. [23] N. Ramakrishnan, An analytical study on strengthening of particulate reinforced metal matrix composites, Acta Mater. 44 (1996) 66-77. [24] B. Peng, H. Zhang, H. Shao, Y. Xu, X. Zhang and H. Zhu, Thermal conductivity of monolayer MoS2, MoSe2 and WS2: interplay of mass effect, interatomic bonding and anharmonicity, RSC Adv. 6 (2016) 5767-5773. [25] A. Zak, L. Sallacan-Ecker, A. Margolin, Y. Feldman, R. Popovitz-Biro, A. Albu-Yaron, M. Genut and R. Tenne, Scaling Up of the WS2 Nanotubes Synthesis, Fullerenes, Nanotubes, Carbon Nanostruct. 19 (2011) 18-26.
11
Table List: Table 1. Chemical composition (in wt%) of the AA6061 alloy Table 2. Recipe of the etching solution used for the preparation of the metallographic specimen Table 3. Grain size of the MMCs with different additives Table 4. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 INT MMCs Table 5. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 IF MMCs Table 6. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 INT MMCs Table 7. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 IF MMCs
12
Figure List: Figure 1. SEM image of AA6061aluminium alloy Figure 2. SEM picture of tungsten disulfide nanotubes (WS2 INT) Figure 3. SEM image of fullerene-like tungsten disulfide (WS2 IF) nanoparticles Figure 4. Schematic rendering of the reactor used for the fabrication of the Al MMCs Figure 5. Ingot sections for metallographic, tensile and hardness tests Figure 6. Metallography of AA6061 MMCs with added (a) 0.1, (b) 0.2 and (c) 0.5 wt.% WS2 INT Figure 7. Metallography of AA6061 MMCs with (a) 0.1 and (b) 0.2 wt.% WS2 IF Figure 8. Grain size analysis of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 9. INT decorating a defect in AA6061/ 0.5 wt.% WS2 INT MMCs Figure 10. Defect of AA6061/ 0.5 wt.% WS2 INT MMCs Figure 11. Hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 12. Stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs Figure 13. Yield strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 14. Ultimate tensile strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 15. Elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles Figure 16. XRD patterns of AA6061/ WS2 INT MMCs Figure 17. XRD patterns of AA6061/ WS2 IF MMCs
13
Si 0.70
Fe 0.09
Table 1. Chemical composition (in wt%) of the AA6061 alloy Cu Mn Mg Cr Zn Ti Al 0.27 0.004 0.90 0.10 0.01 0.008 Bal.
Table 2. Recipe of the etching solution used for the preparation of the metallographic specimen Recipe of etching NaOH (g) Deionized water (ml) Etching time (sec) 5 95 150 Table 3. Grain size of the MMCs with different additives wt.% of INT or IF Grain size (μm) AA6061 0 105.5 0.1 91.6 AA6061/ WS2 INT 0.2 66.9 MMCs 0.5 54.4 0.1 100.0 AA6061/ WS2 IF MMCs 0.2 71.4
Table 4. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 INT MMCs Parameter
Description coefficient of thermal expansion of the matrix coefficient of thermal expansion of the nanoparticles dislocation strengthening coefficient magnitude of the burgers vector average grain size in the composite sample average grain size in the monolithic sample
Value
Reference/note
22 x 10-6℃-1
[21]
15.9 x 10-6℃-1
[22]
1.25 0.286nm
[23] [24]
66.9μm
experimentally determined
105.5μm
experimentally determined
dp
nanotube diameter
70nm
Gm
shear modulus of the matrix
26GPa
Ky
Hall-Petch material constant
0.062MPa√
Tprocess Ttest
processing temperature testing temperature
750℃ 25℃
Vp
volume fraction of nanoparticles
0.00072
σym
yield stress of the matrix
122MPa
αm αp β b dc dm
14
manufacture supplied average nanotube size calculation and experimentally determined calculation and experimentally determined calculated from weight fraction experimentally determined
Table 5. Parameter for reinforcement calculation of AA6061/ 0.2wt.% WS2 IF MMCs Parameter
Description coefficient of thermal expansion of the matrix coefficient of thermal expansion of the nanoparticles dislocation strengthening coefficient magnitude of the burgers vector average grain size in the composite sample average grain size in the monolithic sample
Value
Reference/note
22 x 10-6℃-1
[21]
14.8 x 10-6℃-1
[25]
1.25 0.286nm
[23] [24]
71.4μm
experimentally determined
105.5μm
experimentally determined
dp
fullerene-like diameter
150nm
Gm
shear modulus of the matrix
26GPa
Ky
Hall-Petch material constant
0.062MPa√
Tprocess Ttest
processing temperature testing temperature
750℃ 25℃
Vp
volume fraction of nanoparticles
0.00072
σym
yield stress of the matrix
119MPa
αm αp β b dc dm
calculation and experimentally determined calculation and experimentally determined calculation and experimentally determined calculated from weight fraction experimentally determined
Table 6. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 INT MMCs Percentage of Symbol Description Value (MPa) strengthening contribution enhancement of composite strength 1.54 4.8% due to grain refining enhancement of composite strength 22.25 68.9% Δ due to dislocation density increase enhancement of composite strength 8.45 26.2% Δ due to Orowan strengthening enhancement of composite strength 0.04 0.1% Δ due to load bearing
Table 7. Calculated contributions of the different mechanisms for the reinforcement of the AA6061/ 0.2wt.% WS2 IF MMCs Percentage of Symbol Description Value (MPa) strengthening contribution enhancement of composite strength 1.30 5.8% due to grain refining enhancement of composite strength 16.51 73.6% Δ 15
Δ Δ
due to dislocation density increase enhancement of composite strength due to Orowan strengthening enhancement of composite strength due to load bearing
4.57
20.3%
0.04
0.2%
Figure 1. SEM image of AA6061aluminium alloy
Figure 2. SEM picture of tungsten disulfide nanotubes (WS2 INT)
16
Figure 3. SEM image of fullerene-like tungsten disulfide (WS2 IF) nanoparticles
Figure 4. Schematic rendering of the reactor used for the fabrication of the Al MMCs
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Figure 5. Ingot sections for metallographic, tensile and hardness tests
AA6061-0 wt.% WS2 INT /100x
AA6061-0 wt.% WS2 INT /200x
AA6061-0.1 wt.% WS2 INT /100x
AA6061-0.1 wt.% WS2 INT /200x
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AA6061-0.2 wt.% WS2 INT /100x
AA6061-0.2 wt.% WS2 INT /200x
AA6061-0.5 wt.% WS2 INT /100x
AA6061-0.5 wt.% WS2 INT /200x
Figure 6. Metallography of AA6061 MMCs with added (a) 0.1, (b) 0.2 and (c) 0.5 wt.% WS2 INT
AA6061-0.1 wt.% WS2 IF /100x
AA6061-0.1 wt.% WS2 IF /200x
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AA6061-0.2 wt.% WS2 IF /100x
AA6061-0.2 wt.% WS2 IF /200x
Figure 7. Metallography of AA6061 MMCs with (a) 0.1 and (b) 0.2 wt.% WS2 IF
Figure 8. Grain size analysis of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
Figure 9. INT decorating a defect in AA6061/ 0.5 wt.% WS2 INT MMCs 20
Figure 10. Defect of AA6061/ 0.5 wt.% WS2 INT MMCs
Figure 11. Hardness of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
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Figure 12. Stress-strain curve of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs
Figure 13. Yield strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
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Figure 14. Ultimate tensile strength of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
Figure 15. Elongation of AA6061/ WS2 INT MMCs and AA6061/ WS2 IF MMCs with different concnetrations of the nanotubes/nanoparticles
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Figure 16. XRD patterns of AA6061/ WS2 INT MMCs
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Figure 17. XRD patterns of AA6061/ WS2 IF MMCs
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