Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Experimental Investigations towards Optimization of the Parameters for Wear Loss Quantities in A356/Al₂O₃ Nanocomposites

El-Sayed El-Kady, Tamer Khalil, Tarik Tawfeek*

Mechanical Engineering Department, Faculty of Engineering, Benha University, Cairo, Egypt

Abstract: Metal matrix composites (MMCs) reinforced with nano-particles which called Nanocomposites (MMNCs), are ex-tensively studied in the recent years. Nanocomposites present high strength, wear resistance, hardness and exception- al microstructure stability. The nano-particles can improve the base material in terms of wear resistance, damping properties and mechanical strength. In this paper the tribological behavior of A356/Al₂O₃ nanocomposites were in- vestigated at room temperatures under dry sliding conditions. The results showed that the wear rate of the A356 alloy was significantly improved by the addition of the Al₂O₃ nano-particles. The wear rate of the nanocomposites was re- duced to about 25% (for nanocomposites containing 5 vol.-% of nano-particles) of the wear rate of the A356 mono- lithic alloy.

Keywords: MMCs, MMNCs, A356/Al2O3, nanocomposites, Wear

Received December 19, 2014; Revised December 28, 2014; Accepted January 05, 2015

Citation: El-Sayed El-Kady, Tamer Khalil, Tarik Tawfeek, Experimental Investigations towards Optimization of the Parameters for Wear Loss Quantities in A356/Al₂O₃ Nanocomposites. American Journal of Materials Engineering and Technology, 3 (1). 1-6. January 2015. doi:10.12691/materials-3-1-1

1. Introduction

In the recent years, metal matrix nanocomposites MMNCs have encountered a massive development. MMNCs consists of a metal matrix reinforced with nano-particles; Different species of nano-sized oxides (Al₂O₃, Y₂O₃), nitrides (Si3N4, AlN) carbides (TiC,SiC), hydrates (TiH2) and borides (TiB2) have been employed as reinforcement agents. Especially, carborundum and alumina are the most common ceramic reinforcements for MMNCs. The attractive physical and mechanical properties that can be obtained with MMNCs include high strength, wear resistance, hardness and excep-tional microstructure stability at high temperatures. They are suitable for high-performance applications where cast alloys or precipitation strengthened material cannot be employed due to their limited properties. Moreover, nanocomposite materials ensure performances far superior than alloys strengthened by micro-size particles, Normally, micro-sized ceramic particles are used to improve the yield and ultimate strength of the metal [1-8].

Superior wear resistance is one of the attractive properties in MMNCs. It has been found that particulate-reinforced MMNCs show wear resistance on the order of 10 times higher than the un-reinforced materials in some load ranges. Many studies have been performed in order to understand the effects of various factors on the wear resistance of conventional MMNCs such as the particle size, the fraction of the reinforcing particles, the load, and the sliding speed, on the wear resistance of the particulate-reinforced MMNCs with Al matrices. The reinforcing particles used in these studies are mostly SiC or Al₂O₃ [5,6,7].

Few investigations were reported on the wear behavior of MMNCs [9,10,11] however they are expected that the wear resistance of MMNCs will be higher than the conventional MMCs.

In the present investigation the tribological behavior of A356/Al₂O₃ MMNCs were investigated at room temperatures under dry sliding conditions.

2. Experimental Procedures

2.1. Materials

2.1.1. Matrix

The A356 Al-Si-Mg cast alloy was used as a matrix. The chemical composition of the A356 Al alloy is listed in Table 1.

Table 1. The chemical composition of A356 alloy

2.1.2. Nano-Additives

Nano- Al₂O₃ particulates were used as reinforcing agents. The Al₂O₃ nano-particulates have two different average sizes, typically, 200 and 60 nm. Several metal matrix nanocom-posites (MMNCs) were fabricated with different volume factions of Al2O3 nano-particulates such as 1 vol.-%, 3 vol.-% and 5 vol.-%.

2.2. Nanocomposites Fabrication

The A356/Al₂O₃ nanocomposites were prepared using a combination of rheocasting and squeeze casting techniques. Preparation of the composite alloy was carried out according to the following procedures: About 1 kg of the A356 Al alloy was melted at 680+2°C in a graphite crucible in an electrical resistance furnace. After complete melting and degassing by argon gas of the alloy, the alloy was allowed to cool to the semisolid temperature of 602°C. At such temperature the liquid/solid fraction was about 0.7. The liquid/solid ratio was determined using primary differential scanning calorimeter (DSC) experiments performed on the A356 alloy. A simple mechanical stirrer with three blades made from stainless steel coated with bentonite clay (see Figure 1) was introduced into the melt and stirring was started at approximately 1000 rpm. Before stirring the nano-particles reinforcements after heating to 400°C for two hours were added inside the vortex formed due to stirring. After that, preheated Al₂O₃ nanopar-ticles were introduced into the matrix during the agitation. After completing the addition of Al₂O₃ nanoparticles, the agitation was stopped and the mixture was poured into pre-heated tool steel mould specially designed for this purpose and immediately squeezed during solidification. Figure 2 shows a photograph of the mould used for squeezing the nanocomposites and the ingot after squeezing. The produced ingot has 30 mm diameter and 130+10 mm length.

Figure 1. The three blades stainless steel stirrer

Figure 2. A tool steel mould used to squeeze the nanocompo- sites (a) and the ingot after squeezing (b)

2.2.1. Heat Treatment of Nanocomposites

The nanocomposites were heat treated at T6 before conducting the machining tests. The nanocomposites were solution treated at 540 + 1°C for three hours and then quenched in cold water. After cooling specimens were arti-ficially aged at 160 + 1°C for 12 hours. A schematic dia-gram of the heat treatment process is shown in Figure 3.

The A356/Al₂O₃ MMNCs fabricated in the current in-vestigation exhibited higher hardness values when compared to the unreinforced matrix alloy. The hardness of the MMNCs increases with increasing both the size and volume fraction (up to 3vol-%) of the Al₂O₃ nano-particles. The A356 monolithic alloy exhibited hardness between 38 and 47 VHN. While the MMNCs exhibited a hardness values be-tween 49 and 64 VHN.

Figure 3. A schematic diagram of the solution treatment and artificial aging process

3. Wear Tests

Dry wear tests were carried out on the pin-on-disc wear testing machine shown in Figure 4. The wear tests were carried out at room temperature under several sliding speeds of 0.4, 0.8 and 1.2 m/s. The load was kept constant at 15 N. The chemical composition of the 314 stainless-steel disc was 0.13 wt% C, 1.8 wt% Si, 21.2 wt% Ni, 24.8 wt% Cr, 1.4 wt% Mn and balance Fe.

The wear tests were conducted under dry sliding and oil lubricating conditions. The Mobile 1 Fully Synthetic SEA 15W-50engine oil was used as a lubricant. The synthetic oil should be provided high enough level for lubrication during the test running.

The wear tests were carried out after heat treating the in-vestigated alloys to T6 condition. The specimens used were of a cylindrical shape having a diameter of 8 mm and a length of 12 mm. The specimen’s ends were polished with 1200 grit SiC emery paper and cleaned with acetone. The specimens were then weighted before each experiment on a sensitive balance having sensitivity of 10⁻⁴g. The specimen was fixed on a three jaws clutch. The load was applied to the specimen through a vertical pin fixed with the specimen holder. A fixed track diameter of 100 mm was used in all tests, and a variable sliding time with an interval of 5 min up to 30 min were applied to conduct the wear tests. The duration of the experiment was controlled by a stopwatch. After each ex- periment the specimen is weighed again and the weight loss was calculated.

For each test condition, at least three runs were per-formed. The wear rates (the slopes of the sliding time versus cumulative weight loss curves) of the investigated alloys were calculated by using the data after the run-in stage.

Figure 4. The pin-on-disc wear tester

4. Results & Discussion

Figure 5 shows the variation of the weight loss with slid-ing time for different sliding velocity for the A356 mono-lithic alloy. Figure 6 and Figure 7 show the variation of the weight loss with sliding time for nanocomposites containing 60 nm and 200 nm Al₂O₃ nano-particles for different sliding veloc-ities, respectively.

Figure 5. Variation of the weight loss of the A356 monolithic alloy with sliding time

Figure 6. Variation of the weight loss of the A356/Al2O3 (60 nm) nanocom- posites with sliding time (a) 1 Vol.-%, (b) 3 Vol.-% and (c) 5 Vol.-%

The results revealed that the wear loss of the unreinforced alloy and nanocomposites appears to increase with increas-ing the sliding time. It is noticeable that, at constant applied load, the nanocomposites exhibit lower wear loss compared with the unreinforced alloy. Moreover, it can be seen that the weight loss of the unreinforced alloy and nanocomposites specimens increases with the increase of the sliding velocity. It is clear that mild wear was taken place for both the unre-inforced alloy and nanocomposites. Sever wear region was not observed for both the unreinforced alloy and nanocom-posites.

Figure 8 shows the variation of the wear rate with sliding velocity for the A356/Al₂O₃ nanocomposites containing 60 nm and 200 nm Al₂O₃ nanoparticles. The results showed that, for the unreinforced A356 alloy, increasing the sliding ve-locity increases significantly the wear rate. While for the A356/Al₂O₃ nanocomposites, increasing the sliding velocity increases slightly the wear rates. Such observation was no-ticed for nanocomposites containing 60 nm and 200 nm Al₂O₃ nano-particles. Ithas been found that, at constant sliding velocity and volume fraction, the nanocomposites containing 60 nm of Al₂O₃ nano-particles exhibited slightly lower wear rates than the nanocomposites containing 200 nm of Al₂O₃ nano-particles. At constant nanoparticles size, in-creasing the volume fraction of the nano-particles reduces the wear rates of the nanocomposites (see Figure 9).

Figure 7. Variation of the weight loss of the A356/Al₂O₃ (200 nm) nanocom- posites with sliding time (a) 1 Vol.-%, (b) 3 Vol.-% and (c) 5 Vol.-%

Figure 8. Variation of the wear rate with sliding velocity for the A356/Al2O3 nanocomposites containing (a) 60 nm and (b) 200 nm Al₂O₃ nanoparticles

The results showed that the wear rate of the A356 alloy was significantly improved by the addition of the Al2O3 nanoparticles. The wear rate of the nanocomposites was reduced to about 25% (for nanocomposites containing 5 vol.-% of nanoparticles) of the wear rate of the A356 monolithic alloy. The wear rate of the nanocomposites was slightly influenced by increasing the sliding velocity. In contrast, wear rate of the unreinforced A356 alloy was significantly influenced by the sliding velocity. The wear rate of the nanocomposites was reduced by increasing the volume fraction and/or reducing the Al2O3 nanoparticles size.

For any given nanoparticles content, 1 vol.-%, the mean distance between neighboring nanoparticles for the nano-composite with smaller filler particles (as in 60 nm nano-sized particles) was smaller than that with the bigger particles (200 nm nano-sized particles). For, example, the number of the nanoparticles per unit volume for the nano-composite with 60 nm Al2O3 nanoparticles would be greater than that of the composite with the 200 nm Al2O3 nanopar-ticles.

As the nanoparticles were uniform sized spherical parti-cles, the greater the number of the particles on the worn surface, the larger the contact area between the particles and the contact disc, and hence the better the wear resistance offered by the Al2O3 nanoparticles. That might be a reason for explaining the better improvement of the wear resistance by using nanoparticles.

For the Al unreinforced matrix and the nanocomposites, wear tests performed at temperatures below the transition temperature produced relatively smooth worn surfaces (see Figure 10). SEM examinations of the worn surface of the nanocomposites showed that the worn surfaces were par-tially covered with layers of iron oxide (see Figure 11). The iron oxides can act as solid lubricants and expected to reduce the wear rates with temperature.

The oxide layers (tribolayer) at the contact surfaces were formed as a result of the iron transferred from the counter-face due to the high compressive stresses developed at the interfaces. The compacted tribolayer is harder than the bulk material. During sliding metal–metal wear tests of the nanocomposites, the iron oxide layer formed on the contact surfaces acted as a solid lubricant and improved wear re-sistant. The formation of the tribolayers increased the surface hardness significantly and played an important role in de-laying the mild-to-severe wear transition in aluminum matrix nanocomposites. The presence of Al₂O₃ nano-particles served as a safeguard by generating a hard compacted tri-bolayer with smooth surface and sufficient thickness to protect the material underneath from excessive subsurface damage by forming a physical barrier of about 10 to 50 μm thick with the counterface.

Figure 9. Variation of the wear rate with volume fraction for the A356/Al2O3 nanocomposites at sliding velocity of (a) 0.4 m/s, (b) 0.8 m/s and (c) 1.2 m/s

Figure 10. SEM of the worn surface of A356/5 vol.-% 60 Al₂O₃ nanocompo-sites after 0.5 km at 0.4 m/s

Figure 11. SEM micrograph shows the formation of the iron oxide layer on the worn surface of A356/5 vol.-% 60 nm Al₂O₃ nanocomposites

The reduction of the wear rate of the A356 alloy due to the addition of Al2O3 n nanoparticles may attribute also to the increase of the hardness of the nanocomposites compared with the A356 unreinforced matrix. Increasing the volume fraction of the nanoparticles increases the hardness of the nanocomposites and hence reduces the wear rate of the nanocomposites.

5. Conclusion

According to the results obtained the following conclu-sions can be pointed out:

1. The A356/Al₂O₃ nanocomposites exhibited higher wear resistance at room temperatures when compared with the A356 monolithic alloy. Increasing the volume fraction and/or reducing the Al₂O₃ nanoparticles size improves the wear resistance of the A356/Al₂O₃ nanocomposites.

2. The composites exhibited transition temperature be-tween 150 and 200°C, while the unreinforced alloy exhib-ited a transition temperature between 100 and 150°C.

3. SEM examinations of the worn surface of the nano-composites showed that the worn surfaces were partially covered with layers of iron oxide. The iron oxides can act as solid lubricants and expected to reduce the wear rates with temperature.

References

[1]   | R Casati and M Vedani, Metal Matrix Composites Reinforced byNano-Particles—A Review, Metals (2014), 4, 65-83.
[2]   | N. Soltani et al. “Manufacturing WearResistant 10CeTZP/Al O Nanoparticle Aluminum Composite by Powder Metallurgy Processing”, Materials and Manufactur-ing Processes, 2014, 29 (10).
[3]   | N. Soltani et al. “Effect of hot extrusion on wear properties of Al–15wt.% Mg Si in situ metal matrix composites”, Materials & Design, 2014, 53, 774781.
[4]   | Saka, N., Pamies-Teixeira, J. J. and Suh, N. P., “Wear oft-wo-phase metals”, Wear, (1977), 44, pp. 77-86.
[5]   | Saka, N. and Suh, N. P., “Delamination wear ofdisper-sion-hardened alloys”, Trans. ASME, Ser. B, J.Engng Indust., (1977), 99, pp. 289-294.
[6]   | Debdas Roy, Bikramjit Basu, Amitava Basu Mallick, B.V. Manoj Kumar,Sumit Ghosh, “Understanding the unlubricated friction and wear behavior of Fe-aluminide reinforced Al-based in-situ metal–matrix composite”, Composites: Part A, 37, (2006), pp. 1464-1472.
[7]   | Sheng-ming Zhou, Xiao-bin Zhang, Zhi-peng Ding, Chun-yan Min, Guo-liang Xu, Wen-ming Zhu,“ Fabrication and tribological properties of carbon nanotubes reinforced Al composites prepared by pressurelessinfiltration technique”, Composites: Part A, 38, (2007), pp. 301-306.
[8]   | A. Shafiei-Zarghani, S.F. Kashani-Bozorg, A. Zarei-Hanzaki, “Microstructures and mechanical properties of Al/Al2O3 surface nano-composite layer produced by friction stir pro-cessing”, Materials Science and Engineering A, 500, (2009), pp. 84-91.
[9]   | Straffelini G., Pellizzari M., Molinari A., “Influence of load and temperature on the dry sliding behavior of Al-based metal matrix composites against friction material”, Wear, 256, (2004), pp. 754-763.
[10]   | Singh J., Alpas A.T., “Elevated temperature wear of Al6061 and Al6061-20%Al2O3”, Scripta Metallurgica et Materialia, 32(7), (1995), pp. 1099-1105.
[11]   | Mousavi Abarghouie S.M.R., Seyed Reihani S.M., “Investi-gation of friction and wear behaviors of 2024 Al and 2024 Al/SiCp composite at elevated temperatures’, Journal of Al-loys and Compounds, 501, (2010), pp. 326-332.