Effect of adding iron nano-powder in the physical and mechanical properties in iron parts with micrometric particles.

Vinicius Martins1, a, André Rosiak2,b , Wilson Correa Rodrigues3,c, André Carvalho Tavares4,d and Lírio Schaeffer5,e

1 Instituto Federal Sul-rio-grandense - IFSul – Campus Sapucaia do Sul: Avenida Copacabana, 100 · Bairro Piratini - Sapucaia do Sul/RS · CEP 93.216-120

1,2,3,4,5 Laboratório de Transformação Mecânica - LdTM, Centro de Tecnologia - CT, UFRGS.

Av. Bento Gonçalves, 9500, Agronomia - Porto Alegre, RS, Brazil, CEP 91501-970.a viniciushiper@yahoo.com.br, b andre.rosiak@ufrgs.br, c wilson.rodrigues@ufrgs.br , d

andre.tavares@ufrgs.br, e schaefer@ufrgs.br

Keywords: Effect of addition of nano-powder, physical and mechanical properties

Abstract. This work aims the effect of addition of nano-powder in the physical and mechanical properties of pure iron parts. SEM was performed for the particle morphology of viewing and laser particle size for determining the size of the same. After this procedure was added perceptual lubricant with the metal powder in a mixing "Y" at 22 RPM. Determined the apparent density, compressibility curve and the samples were compacted yielding green densities. It was sintered to 1150 ° C and determined that the physical and mechanical properties using the Archimedes method for determining the density of the sintered samples and the hardness test, micro hardness, metallography and evaluated volumetric shrinkage.

Introduction

Technology in the twenty-first century requires the miniaturization of devices in nanometric sizes, while its ultimate performance is dramatically increased [1]. The general idea was to develop a multi-perspective on nanotechnology leading to recommendations integrated actuation technology at the nanoscale. Public perception of nanotechnology is based on facts and human needs that can be addressed with this technology [2]. The word “Nano” means dwarf, in greek, prefix being used in scientific notation to express a billionth of a meter (10-9). In this size range, a tiny virus, invisible to the naked eye, measuring about 200 nm [3]. When the dimensional size of the material structure decreases, a variety of new phenomena that have never expected in known materials is due to the quantum interaction of particles [4]. Nanoscience and nanotechnology work mainly with the synthesis, characterization, exploration of nanomaterials [5]. Nanotechnology is the ability to understand, control and manipulate matter at the level of atoms and molecules, as well as the level "supramolecular" involving clusters of molecules. Its objective is to create materials, devices and systems with new properties and functions primarily due to its small structure [6]. Nanomaterials are classified as nanostructured materials, nanophase or nano-particle materials. The first material cited are made of grain size on the nanometer scale, while the latter are usually dispersed nanoparticles that form the material. The nano-sized covers a broad range which can be 1 to 200 nm [7]. In addition to materials that are structured by means of control the size, shape and morphological characteristics at the nanoscale, all physical properties, electrical and chemical are altered, such as mechanical or magnetic properties of nanocrystalline materials [8]. Synthesizing and stabilize massive nanocrystalline, material, i.e., polycrystalline materials in the form of a dense mass consistently with sizes below 100 nm in powder form [9]. Nanostructured materials are derived nanomaterials especially nanoparticles, which evolved as a separate class of materials over

the past decade. These types of materials which have at least one dimension on the order less than 100 nm has been widely studied in various areas [10, 11, 12]. The nanostructured materials generally have higher mechanical properties and/or hardness [13, 14, 15], lower ductility and/or toughness [16, 17, 18, 19]. The aim of this study is to evaluate the physical and mechanical behavior of the effect of adding iron nano-powder samples produced with micrometric iron powder.

Materials and Method

To determine the micrometer particle size samples were analyzed under SEM. We used an analytical balance of the Mars brand, with maximum load of 2 kg and resolution of 0.01 g to measure the exact weight of dust and from the mass balance calculation determined the amount of nanosized iron to be added to pure iron. The preparation of the mixture of metal powders through the mixer "Y" were homogenized for 30 minutes at 22 rpm, aiming at further integration of the particles used. The determination of particle size was performed by evaluation of the particle size and morphology with transmission electron microscopy - TEM. The compression of the samples took place in two distinct steps: The first through a cylindrical steel die tempered AISI D6 (Figure 38A) in the hydraulic press of Eka brand with maximum capacity of 40 tons. The compression tooling is the die of 13.0 mm internal diameter (Ø) and 50.0 mm in height (h) along with the lower punch 15 mm in height and the upper punch 60 mm in height. This step the compaction pressure set by the compressibility curve drawn based on standard ASTM B331 [20, 21], and defining the capacity of a certain amount of powder densify under the action of a compression pressure.

Resulted e discuss

Figure 1A shows a micrograph of the powder micrometric there are sub-micrometer particles along with particles smaller than 5 µm and that they are generally spherical due to the atomization process. Figure 1B shows the nano-iron powder.

Figure 1: (A) micrometer pure iron (B) Pure iron nanometer.

The knowledge of the effect of the addition of nano particles of pure iron added compacted samples of micrometer pure iron is important to understand the changes of physical and mechanical properties due to the reduction of the particles. Figure 2 shows the curve of influence of nanometer powder added to micrometric iron powder.

Figure 2: Iron Addition pure nanometer micrometer in Iron

Samples were compacted at 600 MPa to evaluate the influence of the nano-particle. The densities of green vary based on the percentage of nanometer powder added to micrometer powder. The higher the percentage of nanometric particles, the lower the density to green. Is important noted that the powder does not have good flowability, so it was used 1% paraffin wax as a lubricant for the samples with up to 40% of nanometric powder. Samples 50 and 60% of a nanometric powder were used 2% paraffin as samples cracking in compression with the lowest percentage of lubricant. The samples with 70 and 80% nanosized powder were used 3% paraffin and the parts 90 and 100% were placed in 4% lubricant. Figure 3 shows the metallographic sample micrometer iron with 10% nanometer powder to 600 MPa pressure.

Figure 3: Metallography of iron µm with 10% nm [500 X]

It is observed in Figure 3A, that the sample has little porosity visually confirming the achieved density. The attack was performed with 2% Nital identifies two grain sizes in Figure 3B, minors 10 µm and others with 50 µm. It also appears pores 4 µm within grains distributed uniformly over the entire surface. Figure 4 shows the metallographic sample micrometer iron of 20% nanosized.

Figure 4: Metallography of iron µm with 20% nm [500 X]Note in Figure 4A that the sample has little porosity. After the attack of Nital 2% identifies

two grain sizes in Figure 4B, between 10 to 20 µm and other between 50 to 70 µm. It also appears pores between 4 and 5 µm within grains distributed uniformly over the entire surface of the workpiece. Figure 5 shows the metallographic sample micrometer iron with 30% nanometer powder.

Figure 5: Metallography of iron µm with 30% nm [500 X]

There is less porosity than the other metallography and is evenly distributed in the sample appears in Figure 5A and a pore 10 µm, but others are much smaller. Figure 5B shows grain size between 10 to 20 µm and other between 50 to 100 µm. Figure 6 shows the metallographic sample micrometer iron with 40% nanometer powder.

Figure 6: Metallography of iron µm with 40% nm [500 X]

It is observed in Figure 6A, the part has a greater porosity visually as the sample with 30% nano-powder. Was carried out the attack with Nital 2% to identify two grain sizes in Figure 6B, smaller than 10 µm and others with 50 µm. It also appears pores 5 µm within grains distributed uniformly over the entire surface. Little varied porosity and microstructure of the samples with addition of up to 40% of nanometric powder. Figure 7 shows the metallographic sample micrometric iron of 50% nanosized.

Figure 7: Metallography of iron µm with 50% nm [500 X]It is observed in Figure 7A greater porosity which visually confirms the decrease of sintered

density seen in Figure 2. The pores of approximately 10 µm They are more concentrated in some regions of the piece. The decrease in density and porosity increase is due to the addition of a greater volume of lubricant, which need to go out during the heating rate to the sintering level. With the attack of Nital 2% can be observed in Figure 7B grain size 20 to 50 µm with different crystallographic orientations. Figure 8 shows the metallographic sample micrometer iron with 60% nanometer powder.

Figure 8: Metallography of iron µm with 60% nm [500 X]

Note from Figure 8A that the porosity is less than in the sample with 50 % even with the same amount of lubricant as the previous workpiece, then, with the addition of 10% more than nano-powder, this best takes up the gaps left by higher volume of lubricant. The sample attacked exhibits a grain size similar to the other samples with dimension 20 to 50 µm. Figure 9 shows the metallographic sample micrometer iron with 60% nanometer powder.

Figure 9: Metallography of iron µm with 70% nm [500 X]

Figure 9A, shows that the part has a lower porosity than sample visually with 60% the nanometric powder, even with the addition of larger volume of paraffin as a lubricant during

compaction has come to be 3% by mass. With the attack of Nital 2% identify themselves two grain sizes in Figure 9B, lower than 10 µm and others with 50 µm with different crystallographic orientations. Figure 10 show a metallographic sample micrometer iron with 80% nanometer.

Figure 10: Metallography of iron µm with 80% nm [500 X]

In the mixture of 80% iron powder and nano 20% micrometer powder observe the appearance of a second dark phase in Figure 10A and that is not displayed in the sample after attacked. The porosity is less than the sample with 70% which justifies a higher sintered density. The figure 10B It has three different grain sizes. The first dimension less 5 µm, the second was between 10 to 20 µm and third measuring between 40 to 50 µm. Figure 11 shows the metallographic sample micrometer iron with 90% nanometer powder.

Figure 11: Metallography of iron µm with 90% nm [500 X]

The addition of 4% of paraffin as the lubricant for compacting decreased sintered density 6,93 g/cm³ the mix with 80% nano powder 6,71 g/cm³ with 90% nano-powder. The first measuring less than 5 µm, the second was between 10 to 20 µm and the third with size between 40 to 50 µm. The compaction of nanometer iron powder was possible only by adding 4 mass% of paraffin wax as a lubricant. The sintered density was due to the low compressibility of the nanometric powder. The metallographic were performed the samples sintered without attack to show porosity and then immediately put to metalography the same sintered sample attacked with Nital 2% for identifying the points. Figure 12 shows the metallographic sample of pure iron nanometer with pressure 1000 MPa [No attack].

Figure 12: Metallography of pure nano-iron [500x]It is observed in Figure 12 that the sample had a porosity evenly distributed homogeneously.

The attack was carried out with 2% Nital for identification of grain size. Note that if there are two grain sizes, small lie between 5 to 10 µm and the larger grains are 10 to 20 µm, however, identify a dark stage not identified in the outline of the grain. Figure 13 shows the hardness due to the increase of nano-powder.

Figure 13: Microhardness of samples with addition of nanometer iron powder

It is observed that the samples with micrometric iron powder reaches a high hardness due to its high density and compressibility that is greater than nanometric powder. The addition of percentage 10 to 40 % lower the hardness of the samples lying around 80 HV. The addition percentage of 50 to 60% the hardness increases to between 90 to 100 HV. The addition of the percentage of 70 to 100% the nanometer powder raises the average of 135to 150 HV. The density of nanometer pure iron reached a density of 6,47 to 6,75 g/cm³ the pressures of 600 to 1000 MPa.

Conclusions

The study showed the effect of nano-particles of the fine powder, and it was observed that the green densities varied according to the percentage of micrometer to nanometer powder added powder, ranging from 6,7 to 7 g/cm³. The higher the percentage of nanometric particles, the lower the density to green. The powder surface area increases and this means that there is greater need of lubricant to enable compression without fracture of parts. It is important to know the addition of nano powder which increases the hardness of the material due to the increased amount of grain boundaries in the microstructure of parts.

5. Acknowledgements

The authors acknowledge CNPq, CAPES for financing this work.

References

[1] WANG, Z. L. Nanomaterials for Nanoscience and Nanotechnology. Characterization of Nanophase Material. Verlag: CopyrightWiley-VCH Verlag GmbH., 2000. 1 - 132 p.[2] BRUNE, H. et al. Nanotechnology Assessment and Perspectives. Berlin: Springer – Verlag Berlin Heidelberg, 2006. 1 - 493 p. ISBN 3-540-32819-X.[3[ TOMA, H. E. A. A. K. Nanociência e nanotecnologia. Revista CIÊNCIA HOJE, São Paulo, v. 5, n. c, 2005.[4] OHNO, K.; TANAKA, M.; TAKEDA, K. Y. Nano and Micromaterials. New York: Springer – Berlin Heidelberg, 2008. ISBN 978-3-540-74556.[5] KUBO, R. Electronic Properties of Metallic Fine Particles. Journal International the Physical Society of Japan, 1962. 975-986.[6] RAO, C. N. R. E. C. A. K. Nanomaterials Handbook. Boca Raton: Taylor & Francis Group, 2006. 1- 24 p. ISBN 0-8493-2308-8.[7] ROCO, M. C. Nanoscale Science and Engineering:Unifying and Transforming Tools. American Institute of Chemical Engineers, 50, n. 5, May 2004.[8] DUNCAN, D. S. et al. Coulomb-blockade spectroscopy on a small quantum dot in a parallel magnetic field. Applied Physics Letters, 77, 02 OCTOBER 2000. 2183 – 2185.[9] WILDE, G. Nanostructured Materials. Great Britain: Elsevier Ltd, 2009. 1 – 384 p.[10] GOUADEC, G. A. C. P. Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties. Progress in Crystal Growth and Characterization of Materials, 53, 2007. 1–56.[11] NGUYEN, T. P.; HESEMANN, P.; MOREAU, J. J. E. i-Silica: Nanostructured silica hybrid materials containing imidazolium groups by hydrolysis-polycondensation of disilylated bis-N,N0-alkyl-imidazolium halides. Microporous and Mesoporous Materials, França, 2011. 292–300.[12] RAWERS, J.; COOK, D.; KIM, T. Application of Mössbauer spectroscopy in the characterization of nanostructured materials. Materials Science and Engineering A248, 1998. 212–220.[13] GUZ, I. A. et al. Developing the mechanical models for nanomaterials. Composites Part A: Applied Science and Manufacturing, 38, 2007. 1234–1250.[14] KASIAROVÁ, M. et al. Microstructure and fracture-mechanical properties of carbon derivedSi3N4+SiC nanomaterials. Materials Science and Engineering C, 26, July 2006. 862 – 866.[15] ASTHANA, R.; KUMAR, A.; DAHOTRE, N. B. Materials Processing and Manufacturing Science. San Diego: ElsevierAcademic Press, v. 1, 2006. 551-614 p. Chapter 8 – Nanomaterials and Nanomanufacturing.[16] OVID’KO, I. A. A. S. A. G. Enhanced ductility of nanomaterials through optimization of grain boundary sliding and diffusion processes. Acta Materialia, St. Petersburg - Russia, 57, 2009. 2217–2228.[17] HUANG, X.; KAMIKAWA, N.; HANSEN, N. Increasing the ductility of nanostructured Al and Fe by deformation. Materials Science and Engineering A, 493, 2008. 184–189.[18] HAN, B. Q. et al. Effect of strain rate on the ductility of a nanostructured aluminum alloy. Scripta Materialia, 54, 2006. 1175–1180.[19] WANG, Y. M. A. M. E. Strain hardening, strain rate sensitivity, and ductility of nanostructured metals. Materials Science and Engineering A, 375–377, 15 July 2004. 46–52.

[20] ASTM - AMERICAN SOCIETY FOR TESTING AND MATERIALS. ASTM B331 - Compressibility of Metal Powder in Uniaxial Compaction. ASTM - AMERICAN SOCIETY FOR TESTING AND MATERIALS. West Conshohocken, PA. EUA.[21] MPIF - METAL POWDER INDUSTRIES FEDERATION. MPIF Standard 45 - Determination of Compressibility of Metal Powders. MPIF - METAL POWDER INDUSTRIES FEDERATION. Princeton, EUA. 2007.