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Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy
Accepted Manuscript Title: Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy Authors: Ehsan Ghasali, Yahya Palizdar, Ali Jam, Hosein Rajaei, Touradj Ebadzadeh PII: DOI: Reference:
S2352-4928(17)30203-9 https://doi.org/10.1016/j.mtcomm.2017.10.005 MTCOMM 217
To appear in: Received date: Revised date: Accepted date:
14-8-2017 2-10-2017 2-10-2017
Please cite this article as: Ehsan Ghasali, Yahya Palizdar, Ali Jam, Hosein Rajaei, Touradj Ebadzadeh, Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy, Materials Today Communications https://doi.org/10.1016/j.mtcomm.2017.10.005 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 proof before it is published in its final 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.
Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy Ehsan Ghasali *, Yahya Palizdar, Ali Jam, Hosein Rajaei, Touradj Ebadzadeh a
Ceramic Dept, Materials and Energy Research Center, Alborz, Iran
*Corresponding author: Tel : 0098 26 36280040; fax: 0098 26 36201888. E-mail address: [email protected] The highlights of this paper are:
Fe-Al-Mo alloys were prepared by using spark plasma sintering methods. Properties of Fe-Al-Mo alloys can be changed by anneal process. Intermetallic compounds can improve the mechanical properties of prepared specimens.
Abstract The effect of aluminum (Al) and molebdenium (Mo) addition on the phase formation and final properties of iron based alloys has been investigated by powder metallurgy route and spark plasma sintering process. Compounds containing iron (Fe)- 5 wt% Al, Fe-5 wt% Mo and Fe-5 wt% Al and 5 wt% Mo were prepared using a high-energy mixer after milling for 10 minutes. In order to achieve maximum displacement, the sintering process was performed in the temperature range of 600-650°C. Furthermore, the sintered samples were annealed at 1100°C for 2 hours in argon atmosphere. The obtained results indicated that all samples reached to a high enough density at low sintering temperatures and when sintering was performed at high temperatures, the partial melting occurred. The XRD and FESEM investigations revealed the formation of FeMo and AlFe intermetallic and solid solution phases when both Al and Mo additives were used together. Fe-5 wt% Mo-5 wt% Al sample obtained the maximum bending strength (730±31 MPa) and hardness (530±27 Vickers) after sintering at temperature of 630°C. Keywords: Iron; Aluminum; Molybdenum; Spark plasma sintering. 1. Introduction Iron based alloy is one of the important structure alloys in most industries including hightechnology and developed industries and other past manufacturing with traditional processing [1]. In both cases, the presence of little amounts of every element or compound leads to considerable results in final properties of this alloy [2]. From past to now, many investigations have been conducted on the effect of a wide range of additives on the final properties of iron including phase
formation and transitions, heat treatment and etc during casting processes. However, there are a few researches on the effect of additives on the mechanical properties of iron prepared by solid state condition such as powder metallurgy routes [3-5]. The creation and elimination of different phases during producing conditions of two important methods of casting and heat treatment have been investigated in most phase diagrams. However, the powder metallurgy along with heat treatment is a new window to realize the effect of different processing conditions on the microstructure of iron in solid state condition as the most investigated alloy [6, 7]. From this point of view, the use of powder metallurgy in solid state conditions can lead to the formation of submicron regions with uniform distribution. These submicron regions can be assumed as rich or pore zone of reaction between based alloy and additive to form solid solution and intermetallic phases [8]. These reactions have direct effects on the final mechanical properties of samples due to bonding between reaction products and based alloys. It is worth to mention that the final products containing additives are usually known as compounds and solid solutions, by investigation on phase diagrams and transitions. On the other hand, the powder metallurgy technique accompanied by novel and fast sintering process such spark plasma sintering can produce different products far from liquid state process and phases introduced in phase diagrams [9, 11]. In casting methods, the additives such as Cr, Ni, Mo and Co can affect the final properties of iron in a specific way and have positive or negative effect on properties for specific purposes. Sintering process can offer the formation of new intermetallic compounds even for element which accounted as destructive for final properties of iron [12]. The spark plasma sintering can offer many advantages in metallic base specimens as well as other materials under vacuum conditions, surface cleaning, joules heating and application of pressure during sintering process [13, 14]. In SPS, the current passing through between particles in all conductive materials creates sparks and plasma between micron size particles, leading to reduce sintering temperature. Furthermore, using pressure can shorten distance between particles and generate plastic deformation during process. These advantages accompanied by monitoring sintering process using punch displacement offer another unique advantage to nearly reach the final stage of sintering process [15, 16]. To the best of the author’s knowledge, no previous research has been done on the effects of Al and Mo additives on iron alloy using powder metallurgy route combined with spark plasma sintering.
Therefore, the present work investigates the effect of formation of different phases by adding Al and Mo elements on the final microstructure and mechanical properties of Fe alloys. Furthermore, the interfacial reaction was controlled by using post heat treatment at evaluated temperatures to prove the formation of new compounds. 2. Experimental procedures Iron (Merck, 103815, Extra pure), aluminum (Sigma-Aldrich, 202584, 99.9% purity) and molybdenum (Merck 378100, 98% purity) powders were used as starting materials. Three combinations involving additives of 5 wt% Al, 5 wt% Mo and 5 wt% Al+5 wt% Mo were blended with Fe powder using ethanol and these combinations were mixed in a high-energy mixer without protective atmosphere. After 10 minutes, the mixed powders were dried on a hot plate at 70°C using a magnetic stirrer. Then, the mixed powders were inserted directly to a graphite mold (30 mm diameter). The sintering process (SPS-20T-10, China) was performed under high pulsed direct current (between 1000 and 3500 A) in vacuum atmosphere (9 Pa) for 5 min in the temperature range of 600-650 °C with initial and final pressure of 10 and 30 MPa, respectively. After sintering, all samples were grounded and polished to remove graphite layer from the surface of samples. Also a heat treatment was adapted to Fe-5 wt% Al and Fe-5 wt% Mo samples at 1100°C in vacuum atmosphere. The phase identification was carried out using XRD (Philips X0 Pert System) with a Cukα (λ=1.789 A°) radiation source and an image-plate detector over the 2θ range= 10-100° in reflection geometry. The bulk density of sintered samples was measured using the Archimedes’ principle. The three-point bending flexural test was used to examine the strength of sintered samples. The bending strength samples fabricated by SPS were cut from sintered disc with 30 mm diameter. Vickers microhardness values of the sintered samples were calculated using at least ten successive indentations for each sample by a MKV-h21 Microhardness Tester under a load of 1 kg for 15 s. Microstructural characterization of sintered samples was examined using FESEM (MIRA 3 TESCAN, Czech Republic and S360 Cambridge) equipped with an energy dispersive spectrometer (EDS). Details of microstructural investigations and measurement of mechanical properties are the same as reported previously [17]. 3. Results and discussion The sintering behavior of pure Fe and prepared compositions has been shown in Fig. 1. The punch displacement-temperature-time curves are the useful method to investigate sintering stages during
process. Furthermore, the use of derivative displacement rate from displacement Vs sintering changes can be used to identify the effective area of densification during sintering process [18]. As can be observed in Fig. 1, the punch displacement curves have almost similar trends and the total shrinkage for all samples is near 3 mm; however, it seems that the Fe-5Al-5Mo sample shows a higher shrinkage compared to other samples. There are lots of parameters affect the total punch displacement such as graphite foil, heating behavior, time and temperature of applied pressure, reaction products and etc. It seems, since the manual heating procedure was carried out almost in the same way, therefore, small differences between displacement curves can be attributed to the reaction of Al and Mo additives with Fe alloy to form reaction products. However, closer inspection of Fig. 1 reveals another important point that the sintering temperature of all samples is round 630°C and increasing sintering temperature up to 650°C resulted in melting phenomenon. Since higher amount of current flows through Fe particles, therefore, it seems that the Fe powder has a high potential to make spark between particles which makes melting of powder during sintering process. H.W. Zhang [19] has also reported the spark plasma sintering of Fe based alloys at sintering temperatures of about 400, 500 and 600°C. The XRD patterns of prepared samples designed as Fe-5Al and Fe-5Mo after heat treatment are presented in Fig. 2. As can be seen in fig. 2, the dominate peaks are belong to the Fe based alloys for all samples. However, there is a small difference between patterns of Fe-5Al and Fe-Mo and their heat treated types. It was approved that XRD patterns are not reliable to identify reaction products due to small amount of additive. However, XRD patterns can be useful to identify reaction products when considering other evidences such as thermodynamic investigations, research reports and etc. It is worth mentioning that many researchers have been introduced different reaction products for FeAl as well as Fe-Mo system [20-22]. Albert I. Begunov et al [23] studied the thermodynamic stability of intermetallic compounds in aluminum systems. They introduced negative Gibbs free energy for the formation of Al-Fe systems such as FeAl, FeAl2, FeAl3, Fe2Al5 and Fe3Al compounds. Piotr Matysik et al [24] investigated Low-Symmetry Structures from phase equilibrium of Fe-Al Systems. They used SEM and EDS analysis to determine the close composition of Fe-Al system for different at% of aluminum. They proposed the formation of FeAlx compounds which amounts of x increase with increasing at% of aluminum.
As discussed above, the reaction product between Fe and Mo has been reported differently due to different experimental designs and conditions. In the present work, the reaction between Fe and Mo elements resulted in the formation of FeMo compound (magnified area in fig. 2). There have been many reports on the formation of metastable and intermetallic phases in Fe-Mo system, for example, Tohru Watanabe [25] reported the formation of metastable phases during plating method and also intermetallic phases from amorphous and metastable phases after subsequent heat treatment. Y. Jiraskova et al [26] reported the formation of Fe-Mo solid solution accompanied by unsolved Mo after 10 h of milling process for the mixture of Fe and Mo powders. T. Murakami et al [27] studied the microstructure and tribological properties of Fe-Mo alloy- coated on the steel with low pressure plasma spraying. The Fe7Mo6 phase (with composition of Fe-42 at% Mo) was prepared for coating with heating the blended elemental powder at 1473 K for 172.8 ks. The XRD patterns of this work demonstrated FeMo (σ) and Fe7Mo6 (μ) phases with considering to the phase diagram of Fe-Mo system. In another research, T. Murakami et al [28] investigated the spark plasma sintering of Fe-42at%Mo as Fe-Mo alloy system. They proposed the formation of μ phase and excess Mo after sintering of Fe-42 at% Mo at 1200 °C and also dissolving of Mo phase at 1150°C during heat treatment process. With regards to the above mentioned, it seems that the additional peaks observed in XRD patterns of Fe-Mo (fig. 2) can probably be identified as FeMo compound. However, the introduction of phases according to the initial composition and phase diagram is not correct due to the use of powder metallurgy method and the effective parameters such as angle and amounts of contact between powders, diffusion of elements to the extent of reaction elimination, etc. Fig. 3 demonstrates FESEM images of Fe, Al and Mo starting powders and some dark region in Fig. 3a and b related to the existence of iron oxide particles in the initial iron powder. The particle size and distribution of other powders (Al and Mo) can be observed in fig. 3d to g. The microstructure of sintered pure iron in Fig. 4 shows almost fully dense sample without porosities. However, at the first look, dark regions can be mistaken with porosities but according to the EDS investigations, they are iron oxide particles. Besides, the high magnification secondary and back-scattered electron images demonstrated the oxide particles in dark areas (Fig. 4). The existence of iron oxide particles was reported in previous works [28, 29] and two possible sources were related to the formation of these particles: 1) formation of iron oxide during spark plasma process as a result of reaction between iron and oxygen is a low possibility due to vacuum
condition and 2) formation of iron oxide as a result of reaction between iron and air trapped inside the initial iron powder is a high possibility. Fig. 5 and 6 represent backscattered FESEM micrographs of Fe-5 wt% Al and annealed Fe-5 wt% Al specimens, respectively. It is important to note that the formation of FeAl intermetallic compound with some solid solution is observed in the microstructure of spark plasma sintered Fe5 wt% Al sample (Fig. 5). The elemental mapping around dark area showed the diffusion of Fe ions in rich area of Al additive (dark zone) and possible formation of FeAl compound. According to the best of the authors knowledge, a number of research studies have been focused on the formation of intermetallic compound and their relation to the Fe-Al phase diagram [30-32]; but we believe that the powder metallurgy process, non equilibrium condition of sintering and also the effect of contact angle between powders make special condition for elemental diffusion which has direct effect on the formation of solid solution, intermetallic compound and interfacial reaction. Considering to the elemental mapping, three possible events can be derived from Fig. 5: 1) formation of partial solid solution of Fe-Al due to Fe-Al phase diagram potential, 2) formation of FeAl intermetallic compound according to the XRD patterns and previous works and 3) diffusion and reaction between melted aluminum and iron oxide causes the formation of Al2O3 due to the existence of oxygen in the dark areas. Since the sintering process was carried out in vacuum conditions, therefore the possible formation of Al2O3 from reaction between Al and oxygen of the atmosphere is limited or eliminated. To discover each possibility, the samples were annealed and the FESEM results have been indicated in Fig. 6. As can be observed, in some area, the reaction between Al and Fe2O3 has been completed and map analysis shows the formation of Al2O3 and in some other areas the FeAl intermetallic compound has been formed. It seems that the formation of solid solution between Al and Fe was limited at heat treatment temperature of 1100°C and time applied in this process. Fig. 7 and 8 show backscattered FESEM images of Fe-5wt%Mo and annealed Fe-5wt%Mo samples, respectively. As can be demonstrated in fig. 7, the uniform distribution of Mo addition has been observed in the microstructure of specimen. Considering to short sintering time, the reaction between Fe and Mo particles resulted in the formation of FeMo intermetallic compound. As discussed above, the formed interfacial compound with high possibility is FeMo compound. However, the elemental Map analysis demonstrated the existence of Mo in low amounts at matrix and high amounts at the bright areas of specimens. It seems that the formation of solid solution between Mo and Fe is possible, but it is more possible between Al and Fe (Fig. 5) due to higher atomic radius of Mo rather than Al which makes diffusion of Mo more difficult.
To investigate the effect of temperature and time on the formation of interfacial products, the Fe5 wt% Mo was annealed at 1100°C and the microstructure results were shown in Fig. 8. T. Murakami et al [28] studied the friction and wear properties of Fe-Mo intermetallic compounds under oil lubrication. They prepared μ phases samples from the combination of Fe-42 at% Mo according to Fe-Mo phase diagram by using spark plasma sintering at 1100°C and then these samples were annealed at 1050°C. They proposed Fe-42 at% Mo as matrix and some areas rich in Mo as dispersive phase and also showed dissolved Mo phases after annealing process. However in the above-mentioned research, it seems that the annealing process led to encourage interfacial reaction between Fe and Mo and also full diffusion of Fe to the core of Mo phase to form FeMo compounds. It also seems a small amount of precipitation of Mo phase has been occurred around FeMo intermetallic particles which can be considered as side effect of heat treatment and excessive amounts of Mo in interfacial precipitation. It seems that the formation of intermetallic compounds reported by Murakami et al [28] made a new binary system capable of dissolving additional Mo in the matrix, while in our work, the heat treatment process led to the progress of the interfacial reaction. The microstructure of Fe-5 wt% Mo-5 wt% Al specimens (Fig. 9) shows the formation of FeMo compound at the interface of Fe and Mo particles as well as Fe-5 wt% Mo sample. However, in samples containing Al, there is no clear evidence that AlFe compound has been formed but elemental mapping showed limited concentration of Al around Mo particles which implies that this sample contains a higher amount of solid solution. Table 1 shows relative density, bending strength and microhardness of prepared samples. Considering to this table, the maximum relative density has been determined for pure Fe sample and samples sintered in SPS and obtained almost-full density due to the former mentioned advantages of this sintering process. The results of mechanical properties showed that the maximum bending strength and microhardness values were obtained for Fe-5 wt% Mo-5 wt% Al sample. It seems that the presence of Mo and Al accompanied by the capability for intermetallic formation had positive effects on the mechanical properties of Fe-based alloys. Results showed that Mo additive has more positive effects on the final mechanical properties of Fe-based alloy compared to aluminum additive which seems to be due to the formation and amount of FeMo intermetallic compound and also hard nature of Mo rather than Al.
In the case of annealed samples, Fe-5 wt% Mo sample showed increasing in hardness and bending strength compared to Fe-5 wt% Al sample probably due to the progress in interfacial reaction to form FeMo intermetallic compound.
Fig. 10 demonstrates the proposed schematic principle for the formation of FeMo intermetallic compounds during spark plasma sintering process and post heat treatment. With regard to figs. 7 and 8, it can be assumed that the spark between Fe-Fe particles leads to sintering of composite matrix and also spark between Fe-Mo particles results in the formation of a thin layer of FeMo intermetallic compound. The diffusion between particles was activated again after post heat treatment and more interfacial products as intermetallics were formed (fig. 10).
Fig. 11 shows load-extension curves during bending strength test for prepared samples. The fracture toughness can be determined by measuring the absorbed energy before fracture by calculating the area underneath the Load-extension curve as below [34]: 𝐸𝑓
Adsorb energy (J) =∫0 𝐿𝑑𝐸
(1)
where E is Extension, Ef is the Extension up in failure and L is Load. Considering surface area under load-extension as toughness criteria, it can be concluded that the maximum fracture toughness obtains for Fe-5 wt% Mo-5 wt% Al specimen [35, 36]. In samples containing both Mo and Al addition, the fracture toughness decreased in comparison with pure Fe. The fracture toughness increased in both Fe-5 wt% Mo and Fe-5 wt% Al samples after annealing process. On the other hand, Fe-5 wt% Al sample showed a decrease in the fracture load and an increase in the
fracture extension after annealing process. Based on the above mentioned results and discussion, it can be postulated that the annealing process improves the interfacial reaction between Fe and Mo to form FeMo intermetallic compound which leads to increase in fracture toughness of Fe-5 wt% Mo sample. The Fe-5 wt% Al sample showed an increase in fracture toughness, decrease in fracture load and also bending strength (table 1) after heat treatment due to a possible formation of solid solution or melting of Al at 1100°C and/or the aggregation of Al particles in the microstructure of Fe. It is worth mentioning that an increase in fracture extension after annealing process is natural phenomenon due to stress releasing and homogenizing of the microstructure of Fe [37].
4. Conclusions The effect of addition of aluminum and molybdenum on the phase formation, microstructure and mechanical properties of iron based alloys was investigated. Samples were sintered at low temperature by using spark plasma process and obtained near full relative density. The intermetallic compound was formed after sintering of samples containing both aluminum and molybdenum additives. Heat treatment of samples led to the formation of complete FeMo region without excess Mo with improving the reaction between Fe and Mo, however, no reaction was observed in samples containing aluminum. The highest bending strength (730±31 MPa) and microhardness (530±27 Vickers) values were obtained for a sample of Fe-5 wt% Mo-5 wt% Al among all other samples. Furthermore, the comparative fracture toughness determined from bending strength test showed Fe-5 wt% Mo-5 wt% Al sample has a higher fracture toughness compared to other samples.
References [1] McKamey, C. G., et al, A review of recent developments in Fe 3 Al-based alloys, Journal of Materials Research 6.08 (1991): 1779-1805. [2] I.A Choudhury, M.A El-Baradie, Machinability of nickel-base super alloys: a general review, Journal of Materials Processing Technology 77, (1998), 278–284. [3] Wertheim, G. K., V. Jaccarino, J. H. Wernick, and D. N. E. Buchanan. "Range of the exchange interaction in iron alloys." Physical Review Letters 12, no. 1 (1964): 24. [4] Davis, Joseph R., ed. ASM specialty handbook: cast irons. ASM international, 1996. [5] JO, A. "The Manufacture of Iron and Steel: a Handbook for Engineering Students, Merchants, and Users of Iron and Steel." Nature 91 (1913): 186. [6] German, R.M., 1998. Powder metallurgy of iron and steel. John! Wiley & Sons, Inc, 605 Third Ave, New York, NY 10016, USA, 1998. 496. [7] Suryanarayana, C. Non-equilibrium processing of materials. Vol. 2. Elsevier, 1999. [8] Trebin, Hans-Rainer, ed. Quasicrystals: structure and physical properties. John Wiley & Sons, 2006. [9] Ehsan Ghasali, Amir Hossein Pakseresht, Maryam Agheli, Amir Hossein Marzbanpourb, Touradj Ebadzadeha, WC-Co Particles Reinforced Aluminum Matrix by Conventional and Microwave Sintering, 18(6), 2015, pp. 1197-1202. [10] Hudsa Majidian, Ehsan Ghasali, Touradj Ebadzadeh, Mansour Razavi, Effect of heating method on microstructure and mechanical properties of zircon reinforced aluminum composites, Mater. Res. 19 (6) (2016) 1443-1448. [11] H. Shirvanimoghaddam, H. Khayyama, M. Abdizadeh, A.H. KarbalaeiAkbari, A.H.Pakseresht, E.Ghasali, M. Naebe, Boroncarbide reinforced aluminium matrix composite : physical, mechanical characterization and mathematical modelling, Mater. Sci. Eng. A 658 (2016) 135-149. [12] Blair, Malcolm, and Thomas L. Stevens, eds. Steel castings handbook. ASM International, 1995. [13] Ehsan Ghasali, Kamyar Shirvanimoghaddam, Amir Hossein Pakseresht, Masoud Alizadeh, Touradj Ebadzadeh, Evaluation of microstructure and mechanical properties of Al-TaC composites prepared by spark plasma sintering process, Journal of Alloys and Compounds 705 (2017) 283-289.
[14] Ehsan Ghasali, Hossein Nouranian, Ali Rahbari, Houdsa Majidian, Masoud Alizadeh, Touradj Ebadzadeh, Low temperature sintering of aluminum-zircon metal matrix composite prepared by spark plasma sintering, Mater. Res. 19 (5) (2016) 1189-1192. [15] Nouari Saheb et al, Spark Plasma Sintering of Metals and Metal Matrix Nanocomposites: A Review, Journal of Nanomaterials, Volume 2012, Article ID 983470, 13 pages. [16] Ehsan Ghasali, Rahim Yazdani-rad, Keivan Asadian, Touradj Ebadzadeh, Production of Al SiC-TiC hybrid composites using pure and 1056 aluminum powders prepared through microwave and conventional heating methods, J. Alloys Compd. 690 (2017) 512-518. [17] Ehsan Ghasali, Amir Hossein Pakseresht, Masoud Alizadeh, Kamyar Shirvanimoghaddam, Touradj Ebadzadeh, Vanadium carbide reinforced aluminum matrix composite prepared by conventional, microwave and spark plasma sintering, J. Alloys Compd. 688 (2016) 527-533. [18] Ehsan Ghasali, Amirhossein Pakseresht, Fatemeh Safari-kooshali, Maryam Agheli, Touradj Ebadzadeh, Investigation on microstructure and mechanical behavior of Al-ZrB2 composite prepared by microwave and spark plasma sintering, Mater. Sci. Eng. A 627 (2015) 27-30. [19] H.W. Zhang, R. Gopalan, T. Mukai, K. Hono, Fabrication of bulk nanocrystalline Fe–C alloy by spark plasma sintering of mechanically milled powder, Scripta Materialia 53 (2005) 863–868. [20] Ewelina Poche´c, Stanisław Jozwiak, Krzysztof Karczewski, Zbigniew Bojar, Maps of Fe–Al phases formation kinetics parameters during isothermal sintering, Thermochimica Acta 545 (2012) 14– 19. [21] YaHui Liu, XiaoYu Chong, YeHua Jiang, Rong Zhou, Jing Feng, Mechanical properties and electronic structures of Fe-Al intermetallic, Physica B: Condensed Matter 506 (2017): 1-11. [22] M. Bahgat , Min-Kyu Paekb, Jong-Jin Pak, Utilization of mill scale and recycled MoO3 from spent acid for economic synthesis of nanocrystalline intermetallic Fe–Mo alloys, Journal of Alloys and Compounds 477 (2009) 445–449.
[23] Albert I. Begunov and Mikhail P. Kuz’min, Thermodynamic Stability of Intermetallic Compounds in Technical Aluminum, Journal of Siberian Federal University. Engineering & Technologies 2 (2014 7) 132137. [24] Piotr Matysik, Stanisław Jóźwiak and Tomasz Czujko, Characterization of Low-Symmetry Structures from Phase Equilibrium of Fe-Al System—Microstructures and Mechanical Properties, Materials 2015, 8, 914-931; doi:10.3390/ma8030914. [25] Tohru Watanabe, Formation of metastable phases by the plating method, Materials Science and Engineering, A 179/A 180 (1994) 193-197. [26] Y. Jiraskova, K. Zabransky, I. Turek, J. Bursik, D. Jancik, Microstructure and physical properties of mechanically alloyed Fe–Mo powder, Journal of Alloys and Compounds 477 (2009) 55–61.
[27] T. Murakami, S. Sasaki, Microstructure and tribological properties of Fe-Mo alloy-coated steel specimens prepared by low-pressure plasma spraying, Intermetallics 19 (2011) 1873-1877. [28] T. Murakami, K. Kaneda, M. Nakano, H. Mano, A. Korenaga, S. Sasaki, Friction and wear properties of Fe-Mo intermetallic compounds under oil lubrication, Intermetallics 15 (2007) 1573-1581. [29] D Fabrègue, J Piallat, E Maire, Y Jorand, V Massardier-Jourdan , G Bonnefont, (2012) Spark plasma sintering of pure iron nanopowders by simple route, Powder Metallurgy, 55:1, 76-79. [30] S. Jo ´zwiak, K. Karczewski, Influence of aluminum oxides on abrasive wear resistance of Fe–50 at.% Al intermetallic sinters, Journal of Alloys and Compounds 482 (2009) 405–411. [31] Yang Xue, Rujuan Shen, Song Ni, Min Song, Daihong Xiao, Fabrication, microstructure and mechanical properties of Al–Fe intermetallic particle reinforced Al-based composites, Journal of Alloys and Compounds 618 (2015) 537–544. [32] M. RaviathulBasariya, RajatK.Roy, A.K.Pramanick, V.C.Srivastava, N.K. Mukhopadhyay, Structural transition and softening in Al–Fe intermetallic compounds induced by high energy ball milling, Materials Science & Engineering A 638 (2015) 282–288. [33] Cavdar, U., Unlu, B. S., Atik, E. EFFECT OF THE COPPER AMOUNT IN IRON-BASED POWDER-METAL COMPACTS. Materiali in tehnologije, 48(6), 2014, 977-982. [34] M. Karbalaei Akbari, H.R. Baharvandi, K. Shirvanimoghaddam, Tensile and fracture behavior of nano/micro TiB2 particle reinforced casting A356 aluminum alloy composites, Materials and Design 66 (2015) 150–161 [35] Ehsan Ghasali, Masoud Alizadeh, Morteza Niazmand, Touradj Ebadzadeh, Fabrication of magnesiumboron carbide metal matrix composite by powder metallurgy route: comparison between microwave and spark plasma sintering, J. Alloys Compd. 697 (2017) 200-207. [36] Ehsan Ghasali, Rahim Yazdani-rad, Ali Rahbari, Touradj Ebadzadeh, Microwave sintering of aluminum-ZrB2 composite: focusing on microstructure and mechanical properties, J. Mater. Res. 19 (4) (2016) 765e769. [37] Thelning, Karl-Erik. Steel and its heat treatment. Butterworth-Heinemann, 2013. Figure Caption
Fig. 1 Displacement, displacement rate and temperature vs sintering time of specimens: a) Fe, b) Fe-5wt%Al, c) Fe-5wt%Mo and d) Fe-5wt%Al-5wt%Mo.
Fig. 2 XRD patterns of heat treated samples (Fe-5Al and Fe-5Mo) and sintered samples (Fe-5Al, Fe-5Mo and Fe-5Al-5Mo)
Fig. 3 FESEM images of starting powders: a, b) Fe, c, d) Al and e, f) Mo
Fig. 4 Backscattered FESEM micrographs of sintered Fe sample
Fig. 5 FESEM images and elemental map analysis of Fe-5 wt% Al sample
Fig. 6 FESEM images and elemental map analysis of Fe-Al sample after heat treatment at 1100°C (annealed Fe-5 wt% Al)
Fig. 7 FESEM images and elemental MAP analysis of Fe-5Mo sample
Fig. 8 FESEM images and elemental map analysis of Fe-5 wt% Mo sample after heat treatment at 1100°C (annealed Fe-5 Mo)
Fig. 9 FESEM images and elemental map analysis of Fe-5 wt% Mo-5 wt% Al sample
Fig. 10 Schematic principle of the formation of FeMo intermetallic compounds during sintering process and post heat treatment
Fig. 11 Load-Extension curves of sintered and heat treated samples during bending strength test
Table 1 Physical and mechanical properties of sintered and heat treated iron alloys samples Relative density * Bending strength Microhardness (%) (MPa) (Vickers) Fe
99.8±0.1%
400±12
320±8
Fe-5Al
99.5±0.1%
510±17
386±23
Fe-5Al (anneal)
99.6±0.1%
480±10
350±25
Fe-5Mo
99.6±0.5%
621±21
572±42
Fe-5Mo (anneal)
99.6±0.5%
670±11
630±31
Fe-5Al-5Mo
99.7±0.2%
730±31
530±27
* Note: The amounts of interfacial products were not considered in the relative density calculation.
S2352-4928(17)30203-9 https://doi.org/10.1016/j.mtcomm.2017.10.005 MTCOMM 217
To appear in: Received date: Revised date: Accepted date:
14-8-2017 2-10-2017 2-10-2017
Please cite this article as: Ehsan Ghasali, Yahya Palizdar, Ali Jam, Hosein Rajaei, Touradj Ebadzadeh, Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy, Materials Today Communications https://doi.org/10.1016/j.mtcomm.2017.10.005 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 proof before it is published in its final 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.
Effect of Al and Mo addition on phase formation, mechanical and microstructure properties of spark plasma sintered iron alloy Ehsan Ghasali *, Yahya Palizdar, Ali Jam, Hosein Rajaei, Touradj Ebadzadeh a
Ceramic Dept, Materials and Energy Research Center, Alborz, Iran
*Corresponding author: Tel : 0098 26 36280040; fax: 0098 26 36201888. E-mail address: [email protected] The highlights of this paper are:
Fe-Al-Mo alloys were prepared by using spark plasma sintering methods. Properties of Fe-Al-Mo alloys can be changed by anneal process. Intermetallic compounds can improve the mechanical properties of prepared specimens.
Abstract The effect of aluminum (Al) and molebdenium (Mo) addition on the phase formation and final properties of iron based alloys has been investigated by powder metallurgy route and spark plasma sintering process. Compounds containing iron (Fe)- 5 wt% Al, Fe-5 wt% Mo and Fe-5 wt% Al and 5 wt% Mo were prepared using a high-energy mixer after milling for 10 minutes. In order to achieve maximum displacement, the sintering process was performed in the temperature range of 600-650°C. Furthermore, the sintered samples were annealed at 1100°C for 2 hours in argon atmosphere. The obtained results indicated that all samples reached to a high enough density at low sintering temperatures and when sintering was performed at high temperatures, the partial melting occurred. The XRD and FESEM investigations revealed the formation of FeMo and AlFe intermetallic and solid solution phases when both Al and Mo additives were used together. Fe-5 wt% Mo-5 wt% Al sample obtained the maximum bending strength (730±31 MPa) and hardness (530±27 Vickers) after sintering at temperature of 630°C. Keywords: Iron; Aluminum; Molybdenum; Spark plasma sintering. 1. Introduction Iron based alloy is one of the important structure alloys in most industries including hightechnology and developed industries and other past manufacturing with traditional processing [1]. In both cases, the presence of little amounts of every element or compound leads to considerable results in final properties of this alloy [2]. From past to now, many investigations have been conducted on the effect of a wide range of additives on the final properties of iron including phase
formation and transitions, heat treatment and etc during casting processes. However, there are a few researches on the effect of additives on the mechanical properties of iron prepared by solid state condition such as powder metallurgy routes [3-5]. The creation and elimination of different phases during producing conditions of two important methods of casting and heat treatment have been investigated in most phase diagrams. However, the powder metallurgy along with heat treatment is a new window to realize the effect of different processing conditions on the microstructure of iron in solid state condition as the most investigated alloy [6, 7]. From this point of view, the use of powder metallurgy in solid state conditions can lead to the formation of submicron regions with uniform distribution. These submicron regions can be assumed as rich or pore zone of reaction between based alloy and additive to form solid solution and intermetallic phases [8]. These reactions have direct effects on the final mechanical properties of samples due to bonding between reaction products and based alloys. It is worth to mention that the final products containing additives are usually known as compounds and solid solutions, by investigation on phase diagrams and transitions. On the other hand, the powder metallurgy technique accompanied by novel and fast sintering process such spark plasma sintering can produce different products far from liquid state process and phases introduced in phase diagrams [9, 11]. In casting methods, the additives such as Cr, Ni, Mo and Co can affect the final properties of iron in a specific way and have positive or negative effect on properties for specific purposes. Sintering process can offer the formation of new intermetallic compounds even for element which accounted as destructive for final properties of iron [12]. The spark plasma sintering can offer many advantages in metallic base specimens as well as other materials under vacuum conditions, surface cleaning, joules heating and application of pressure during sintering process [13, 14]. In SPS, the current passing through between particles in all conductive materials creates sparks and plasma between micron size particles, leading to reduce sintering temperature. Furthermore, using pressure can shorten distance between particles and generate plastic deformation during process. These advantages accompanied by monitoring sintering process using punch displacement offer another unique advantage to nearly reach the final stage of sintering process [15, 16]. To the best of the author’s knowledge, no previous research has been done on the effects of Al and Mo additives on iron alloy using powder metallurgy route combined with spark plasma sintering.
Therefore, the present work investigates the effect of formation of different phases by adding Al and Mo elements on the final microstructure and mechanical properties of Fe alloys. Furthermore, the interfacial reaction was controlled by using post heat treatment at evaluated temperatures to prove the formation of new compounds. 2. Experimental procedures Iron (Merck, 103815, Extra pure), aluminum (Sigma-Aldrich, 202584, 99.9% purity) and molybdenum (Merck 378100, 98% purity) powders were used as starting materials. Three combinations involving additives of 5 wt% Al, 5 wt% Mo and 5 wt% Al+5 wt% Mo were blended with Fe powder using ethanol and these combinations were mixed in a high-energy mixer without protective atmosphere. After 10 minutes, the mixed powders were dried on a hot plate at 70°C using a magnetic stirrer. Then, the mixed powders were inserted directly to a graphite mold (30 mm diameter). The sintering process (SPS-20T-10, China) was performed under high pulsed direct current (between 1000 and 3500 A) in vacuum atmosphere (9 Pa) for 5 min in the temperature range of 600-650 °C with initial and final pressure of 10 and 30 MPa, respectively. After sintering, all samples were grounded and polished to remove graphite layer from the surface of samples. Also a heat treatment was adapted to Fe-5 wt% Al and Fe-5 wt% Mo samples at 1100°C in vacuum atmosphere. The phase identification was carried out using XRD (Philips X0 Pert System) with a Cukα (λ=1.789 A°) radiation source and an image-plate detector over the 2θ range= 10-100° in reflection geometry. The bulk density of sintered samples was measured using the Archimedes’ principle. The three-point bending flexural test was used to examine the strength of sintered samples. The bending strength samples fabricated by SPS were cut from sintered disc with 30 mm diameter. Vickers microhardness values of the sintered samples were calculated using at least ten successive indentations for each sample by a MKV-h21 Microhardness Tester under a load of 1 kg for 15 s. Microstructural characterization of sintered samples was examined using FESEM (MIRA 3 TESCAN, Czech Republic and S360 Cambridge) equipped with an energy dispersive spectrometer (EDS). Details of microstructural investigations and measurement of mechanical properties are the same as reported previously [17]. 3. Results and discussion The sintering behavior of pure Fe and prepared compositions has been shown in Fig. 1. The punch displacement-temperature-time curves are the useful method to investigate sintering stages during
process. Furthermore, the use of derivative displacement rate from displacement Vs sintering changes can be used to identify the effective area of densification during sintering process [18]. As can be observed in Fig. 1, the punch displacement curves have almost similar trends and the total shrinkage for all samples is near 3 mm; however, it seems that the Fe-5Al-5Mo sample shows a higher shrinkage compared to other samples. There are lots of parameters affect the total punch displacement such as graphite foil, heating behavior, time and temperature of applied pressure, reaction products and etc. It seems, since the manual heating procedure was carried out almost in the same way, therefore, small differences between displacement curves can be attributed to the reaction of Al and Mo additives with Fe alloy to form reaction products. However, closer inspection of Fig. 1 reveals another important point that the sintering temperature of all samples is round 630°C and increasing sintering temperature up to 650°C resulted in melting phenomenon. Since higher amount of current flows through Fe particles, therefore, it seems that the Fe powder has a high potential to make spark between particles which makes melting of powder during sintering process. H.W. Zhang [19] has also reported the spark plasma sintering of Fe based alloys at sintering temperatures of about 400, 500 and 600°C. The XRD patterns of prepared samples designed as Fe-5Al and Fe-5Mo after heat treatment are presented in Fig. 2. As can be seen in fig. 2, the dominate peaks are belong to the Fe based alloys for all samples. However, there is a small difference between patterns of Fe-5Al and Fe-Mo and their heat treated types. It was approved that XRD patterns are not reliable to identify reaction products due to small amount of additive. However, XRD patterns can be useful to identify reaction products when considering other evidences such as thermodynamic investigations, research reports and etc. It is worth mentioning that many researchers have been introduced different reaction products for FeAl as well as Fe-Mo system [20-22]. Albert I. Begunov et al [23] studied the thermodynamic stability of intermetallic compounds in aluminum systems. They introduced negative Gibbs free energy for the formation of Al-Fe systems such as FeAl, FeAl2, FeAl3, Fe2Al5 and Fe3Al compounds. Piotr Matysik et al [24] investigated Low-Symmetry Structures from phase equilibrium of Fe-Al Systems. They used SEM and EDS analysis to determine the close composition of Fe-Al system for different at% of aluminum. They proposed the formation of FeAlx compounds which amounts of x increase with increasing at% of aluminum.
As discussed above, the reaction product between Fe and Mo has been reported differently due to different experimental designs and conditions. In the present work, the reaction between Fe and Mo elements resulted in the formation of FeMo compound (magnified area in fig. 2). There have been many reports on the formation of metastable and intermetallic phases in Fe-Mo system, for example, Tohru Watanabe [25] reported the formation of metastable phases during plating method and also intermetallic phases from amorphous and metastable phases after subsequent heat treatment. Y. Jiraskova et al [26] reported the formation of Fe-Mo solid solution accompanied by unsolved Mo after 10 h of milling process for the mixture of Fe and Mo powders. T. Murakami et al [27] studied the microstructure and tribological properties of Fe-Mo alloy- coated on the steel with low pressure plasma spraying. The Fe7Mo6 phase (with composition of Fe-42 at% Mo) was prepared for coating with heating the blended elemental powder at 1473 K for 172.8 ks. The XRD patterns of this work demonstrated FeMo (σ) and Fe7Mo6 (μ) phases with considering to the phase diagram of Fe-Mo system. In another research, T. Murakami et al [28] investigated the spark plasma sintering of Fe-42at%Mo as Fe-Mo alloy system. They proposed the formation of μ phase and excess Mo after sintering of Fe-42 at% Mo at 1200 °C and also dissolving of Mo phase at 1150°C during heat treatment process. With regards to the above mentioned, it seems that the additional peaks observed in XRD patterns of Fe-Mo (fig. 2) can probably be identified as FeMo compound. However, the introduction of phases according to the initial composition and phase diagram is not correct due to the use of powder metallurgy method and the effective parameters such as angle and amounts of contact between powders, diffusion of elements to the extent of reaction elimination, etc. Fig. 3 demonstrates FESEM images of Fe, Al and Mo starting powders and some dark region in Fig. 3a and b related to the existence of iron oxide particles in the initial iron powder. The particle size and distribution of other powders (Al and Mo) can be observed in fig. 3d to g. The microstructure of sintered pure iron in Fig. 4 shows almost fully dense sample without porosities. However, at the first look, dark regions can be mistaken with porosities but according to the EDS investigations, they are iron oxide particles. Besides, the high magnification secondary and back-scattered electron images demonstrated the oxide particles in dark areas (Fig. 4). The existence of iron oxide particles was reported in previous works [28, 29] and two possible sources were related to the formation of these particles: 1) formation of iron oxide during spark plasma process as a result of reaction between iron and oxygen is a low possibility due to vacuum
condition and 2) formation of iron oxide as a result of reaction between iron and air trapped inside the initial iron powder is a high possibility. Fig. 5 and 6 represent backscattered FESEM micrographs of Fe-5 wt% Al and annealed Fe-5 wt% Al specimens, respectively. It is important to note that the formation of FeAl intermetallic compound with some solid solution is observed in the microstructure of spark plasma sintered Fe5 wt% Al sample (Fig. 5). The elemental mapping around dark area showed the diffusion of Fe ions in rich area of Al additive (dark zone) and possible formation of FeAl compound. According to the best of the authors knowledge, a number of research studies have been focused on the formation of intermetallic compound and their relation to the Fe-Al phase diagram [30-32]; but we believe that the powder metallurgy process, non equilibrium condition of sintering and also the effect of contact angle between powders make special condition for elemental diffusion which has direct effect on the formation of solid solution, intermetallic compound and interfacial reaction. Considering to the elemental mapping, three possible events can be derived from Fig. 5: 1) formation of partial solid solution of Fe-Al due to Fe-Al phase diagram potential, 2) formation of FeAl intermetallic compound according to the XRD patterns and previous works and 3) diffusion and reaction between melted aluminum and iron oxide causes the formation of Al2O3 due to the existence of oxygen in the dark areas. Since the sintering process was carried out in vacuum conditions, therefore the possible formation of Al2O3 from reaction between Al and oxygen of the atmosphere is limited or eliminated. To discover each possibility, the samples were annealed and the FESEM results have been indicated in Fig. 6. As can be observed, in some area, the reaction between Al and Fe2O3 has been completed and map analysis shows the formation of Al2O3 and in some other areas the FeAl intermetallic compound has been formed. It seems that the formation of solid solution between Al and Fe was limited at heat treatment temperature of 1100°C and time applied in this process. Fig. 7 and 8 show backscattered FESEM images of Fe-5wt%Mo and annealed Fe-5wt%Mo samples, respectively. As can be demonstrated in fig. 7, the uniform distribution of Mo addition has been observed in the microstructure of specimen. Considering to short sintering time, the reaction between Fe and Mo particles resulted in the formation of FeMo intermetallic compound. As discussed above, the formed interfacial compound with high possibility is FeMo compound. However, the elemental Map analysis demonstrated the existence of Mo in low amounts at matrix and high amounts at the bright areas of specimens. It seems that the formation of solid solution between Mo and Fe is possible, but it is more possible between Al and Fe (Fig. 5) due to higher atomic radius of Mo rather than Al which makes diffusion of Mo more difficult.
To investigate the effect of temperature and time on the formation of interfacial products, the Fe5 wt% Mo was annealed at 1100°C and the microstructure results were shown in Fig. 8. T. Murakami et al [28] studied the friction and wear properties of Fe-Mo intermetallic compounds under oil lubrication. They prepared μ phases samples from the combination of Fe-42 at% Mo according to Fe-Mo phase diagram by using spark plasma sintering at 1100°C and then these samples were annealed at 1050°C. They proposed Fe-42 at% Mo as matrix and some areas rich in Mo as dispersive phase and also showed dissolved Mo phases after annealing process. However in the above-mentioned research, it seems that the annealing process led to encourage interfacial reaction between Fe and Mo and also full diffusion of Fe to the core of Mo phase to form FeMo compounds. It also seems a small amount of precipitation of Mo phase has been occurred around FeMo intermetallic particles which can be considered as side effect of heat treatment and excessive amounts of Mo in interfacial precipitation. It seems that the formation of intermetallic compounds reported by Murakami et al [28] made a new binary system capable of dissolving additional Mo in the matrix, while in our work, the heat treatment process led to the progress of the interfacial reaction. The microstructure of Fe-5 wt% Mo-5 wt% Al specimens (Fig. 9) shows the formation of FeMo compound at the interface of Fe and Mo particles as well as Fe-5 wt% Mo sample. However, in samples containing Al, there is no clear evidence that AlFe compound has been formed but elemental mapping showed limited concentration of Al around Mo particles which implies that this sample contains a higher amount of solid solution. Table 1 shows relative density, bending strength and microhardness of prepared samples. Considering to this table, the maximum relative density has been determined for pure Fe sample and samples sintered in SPS and obtained almost-full density due to the former mentioned advantages of this sintering process. The results of mechanical properties showed that the maximum bending strength and microhardness values were obtained for Fe-5 wt% Mo-5 wt% Al sample. It seems that the presence of Mo and Al accompanied by the capability for intermetallic formation had positive effects on the mechanical properties of Fe-based alloys. Results showed that Mo additive has more positive effects on the final mechanical properties of Fe-based alloy compared to aluminum additive which seems to be due to the formation and amount of FeMo intermetallic compound and also hard nature of Mo rather than Al.
In the case of annealed samples, Fe-5 wt% Mo sample showed increasing in hardness and bending strength compared to Fe-5 wt% Al sample probably due to the progress in interfacial reaction to form FeMo intermetallic compound.
Fig. 10 demonstrates the proposed schematic principle for the formation of FeMo intermetallic compounds during spark plasma sintering process and post heat treatment. With regard to figs. 7 and 8, it can be assumed that the spark between Fe-Fe particles leads to sintering of composite matrix and also spark between Fe-Mo particles results in the formation of a thin layer of FeMo intermetallic compound. The diffusion between particles was activated again after post heat treatment and more interfacial products as intermetallics were formed (fig. 10).
Fig. 11 shows load-extension curves during bending strength test for prepared samples. The fracture toughness can be determined by measuring the absorbed energy before fracture by calculating the area underneath the Load-extension curve as below [34]: 𝐸𝑓
Adsorb energy (J) =∫0 𝐿𝑑𝐸
(1)
where E is Extension, Ef is the Extension up in failure and L is Load. Considering surface area under load-extension as toughness criteria, it can be concluded that the maximum fracture toughness obtains for Fe-5 wt% Mo-5 wt% Al specimen [35, 36]. In samples containing both Mo and Al addition, the fracture toughness decreased in comparison with pure Fe. The fracture toughness increased in both Fe-5 wt% Mo and Fe-5 wt% Al samples after annealing process. On the other hand, Fe-5 wt% Al sample showed a decrease in the fracture load and an increase in the
fracture extension after annealing process. Based on the above mentioned results and discussion, it can be postulated that the annealing process improves the interfacial reaction between Fe and Mo to form FeMo intermetallic compound which leads to increase in fracture toughness of Fe-5 wt% Mo sample. The Fe-5 wt% Al sample showed an increase in fracture toughness, decrease in fracture load and also bending strength (table 1) after heat treatment due to a possible formation of solid solution or melting of Al at 1100°C and/or the aggregation of Al particles in the microstructure of Fe. It is worth mentioning that an increase in fracture extension after annealing process is natural phenomenon due to stress releasing and homogenizing of the microstructure of Fe [37].
4. Conclusions The effect of addition of aluminum and molybdenum on the phase formation, microstructure and mechanical properties of iron based alloys was investigated. Samples were sintered at low temperature by using spark plasma process and obtained near full relative density. The intermetallic compound was formed after sintering of samples containing both aluminum and molybdenum additives. Heat treatment of samples led to the formation of complete FeMo region without excess Mo with improving the reaction between Fe and Mo, however, no reaction was observed in samples containing aluminum. The highest bending strength (730±31 MPa) and microhardness (530±27 Vickers) values were obtained for a sample of Fe-5 wt% Mo-5 wt% Al among all other samples. Furthermore, the comparative fracture toughness determined from bending strength test showed Fe-5 wt% Mo-5 wt% Al sample has a higher fracture toughness compared to other samples.
References [1] McKamey, C. G., et al, A review of recent developments in Fe 3 Al-based alloys, Journal of Materials Research 6.08 (1991): 1779-1805. [2] I.A Choudhury, M.A El-Baradie, Machinability of nickel-base super alloys: a general review, Journal of Materials Processing Technology 77, (1998), 278–284. [3] Wertheim, G. K., V. Jaccarino, J. H. Wernick, and D. N. E. Buchanan. "Range of the exchange interaction in iron alloys." Physical Review Letters 12, no. 1 (1964): 24. [4] Davis, Joseph R., ed. ASM specialty handbook: cast irons. ASM international, 1996. [5] JO, A. "The Manufacture of Iron and Steel: a Handbook for Engineering Students, Merchants, and Users of Iron and Steel." Nature 91 (1913): 186. [6] German, R.M., 1998. Powder metallurgy of iron and steel. John! Wiley & Sons, Inc, 605 Third Ave, New York, NY 10016, USA, 1998. 496. [7] Suryanarayana, C. Non-equilibrium processing of materials. Vol. 2. Elsevier, 1999. [8] Trebin, Hans-Rainer, ed. Quasicrystals: structure and physical properties. John Wiley & Sons, 2006. [9] Ehsan Ghasali, Amir Hossein Pakseresht, Maryam Agheli, Amir Hossein Marzbanpourb, Touradj Ebadzadeha, WC-Co Particles Reinforced Aluminum Matrix by Conventional and Microwave Sintering, 18(6), 2015, pp. 1197-1202. [10] Hudsa Majidian, Ehsan Ghasali, Touradj Ebadzadeh, Mansour Razavi, Effect of heating method on microstructure and mechanical properties of zircon reinforced aluminum composites, Mater. Res. 19 (6) (2016) 1443-1448. [11] H. Shirvanimoghaddam, H. Khayyama, M. Abdizadeh, A.H. KarbalaeiAkbari, A.H.Pakseresht, E.Ghasali, M. Naebe, Boroncarbide reinforced aluminium matrix composite : physical, mechanical characterization and mathematical modelling, Mater. Sci. Eng. A 658 (2016) 135-149. [12] Blair, Malcolm, and Thomas L. Stevens, eds. Steel castings handbook. ASM International, 1995. [13] Ehsan Ghasali, Kamyar Shirvanimoghaddam, Amir Hossein Pakseresht, Masoud Alizadeh, Touradj Ebadzadeh, Evaluation of microstructure and mechanical properties of Al-TaC composites prepared by spark plasma sintering process, Journal of Alloys and Compounds 705 (2017) 283-289.
[14] Ehsan Ghasali, Hossein Nouranian, Ali Rahbari, Houdsa Majidian, Masoud Alizadeh, Touradj Ebadzadeh, Low temperature sintering of aluminum-zircon metal matrix composite prepared by spark plasma sintering, Mater. Res. 19 (5) (2016) 1189-1192. [15] Nouari Saheb et al, Spark Plasma Sintering of Metals and Metal Matrix Nanocomposites: A Review, Journal of Nanomaterials, Volume 2012, Article ID 983470, 13 pages. [16] Ehsan Ghasali, Rahim Yazdani-rad, Keivan Asadian, Touradj Ebadzadeh, Production of Al SiC-TiC hybrid composites using pure and 1056 aluminum powders prepared through microwave and conventional heating methods, J. Alloys Compd. 690 (2017) 512-518. [17] Ehsan Ghasali, Amir Hossein Pakseresht, Masoud Alizadeh, Kamyar Shirvanimoghaddam, Touradj Ebadzadeh, Vanadium carbide reinforced aluminum matrix composite prepared by conventional, microwave and spark plasma sintering, J. Alloys Compd. 688 (2016) 527-533. [18] Ehsan Ghasali, Amirhossein Pakseresht, Fatemeh Safari-kooshali, Maryam Agheli, Touradj Ebadzadeh, Investigation on microstructure and mechanical behavior of Al-ZrB2 composite prepared by microwave and spark plasma sintering, Mater. Sci. Eng. A 627 (2015) 27-30. [19] H.W. Zhang, R. Gopalan, T. Mukai, K. Hono, Fabrication of bulk nanocrystalline Fe–C alloy by spark plasma sintering of mechanically milled powder, Scripta Materialia 53 (2005) 863–868. [20] Ewelina Poche´c, Stanisław Jozwiak, Krzysztof Karczewski, Zbigniew Bojar, Maps of Fe–Al phases formation kinetics parameters during isothermal sintering, Thermochimica Acta 545 (2012) 14– 19. [21] YaHui Liu, XiaoYu Chong, YeHua Jiang, Rong Zhou, Jing Feng, Mechanical properties and electronic structures of Fe-Al intermetallic, Physica B: Condensed Matter 506 (2017): 1-11. [22] M. Bahgat , Min-Kyu Paekb, Jong-Jin Pak, Utilization of mill scale and recycled MoO3 from spent acid for economic synthesis of nanocrystalline intermetallic Fe–Mo alloys, Journal of Alloys and Compounds 477 (2009) 445–449.
[23] Albert I. Begunov and Mikhail P. Kuz’min, Thermodynamic Stability of Intermetallic Compounds in Technical Aluminum, Journal of Siberian Federal University. Engineering & Technologies 2 (2014 7) 132137. [24] Piotr Matysik, Stanisław Jóźwiak and Tomasz Czujko, Characterization of Low-Symmetry Structures from Phase Equilibrium of Fe-Al System—Microstructures and Mechanical Properties, Materials 2015, 8, 914-931; doi:10.3390/ma8030914. [25] Tohru Watanabe, Formation of metastable phases by the plating method, Materials Science and Engineering, A 179/A 180 (1994) 193-197. [26] Y. Jiraskova, K. Zabransky, I. Turek, J. Bursik, D. Jancik, Microstructure and physical properties of mechanically alloyed Fe–Mo powder, Journal of Alloys and Compounds 477 (2009) 55–61.
[27] T. Murakami, S. Sasaki, Microstructure and tribological properties of Fe-Mo alloy-coated steel specimens prepared by low-pressure plasma spraying, Intermetallics 19 (2011) 1873-1877. [28] T. Murakami, K. Kaneda, M. Nakano, H. Mano, A. Korenaga, S. Sasaki, Friction and wear properties of Fe-Mo intermetallic compounds under oil lubrication, Intermetallics 15 (2007) 1573-1581. [29] D Fabrègue, J Piallat, E Maire, Y Jorand, V Massardier-Jourdan , G Bonnefont, (2012) Spark plasma sintering of pure iron nanopowders by simple route, Powder Metallurgy, 55:1, 76-79. [30] S. Jo ´zwiak, K. Karczewski, Influence of aluminum oxides on abrasive wear resistance of Fe–50 at.% Al intermetallic sinters, Journal of Alloys and Compounds 482 (2009) 405–411. [31] Yang Xue, Rujuan Shen, Song Ni, Min Song, Daihong Xiao, Fabrication, microstructure and mechanical properties of Al–Fe intermetallic particle reinforced Al-based composites, Journal of Alloys and Compounds 618 (2015) 537–544. [32] M. RaviathulBasariya, RajatK.Roy, A.K.Pramanick, V.C.Srivastava, N.K. Mukhopadhyay, Structural transition and softening in Al–Fe intermetallic compounds induced by high energy ball milling, Materials Science & Engineering A 638 (2015) 282–288. [33] Cavdar, U., Unlu, B. S., Atik, E. EFFECT OF THE COPPER AMOUNT IN IRON-BASED POWDER-METAL COMPACTS. Materiali in tehnologije, 48(6), 2014, 977-982. [34] M. Karbalaei Akbari, H.R. Baharvandi, K. Shirvanimoghaddam, Tensile and fracture behavior of nano/micro TiB2 particle reinforced casting A356 aluminum alloy composites, Materials and Design 66 (2015) 150–161 [35] Ehsan Ghasali, Masoud Alizadeh, Morteza Niazmand, Touradj Ebadzadeh, Fabrication of magnesiumboron carbide metal matrix composite by powder metallurgy route: comparison between microwave and spark plasma sintering, J. Alloys Compd. 697 (2017) 200-207. [36] Ehsan Ghasali, Rahim Yazdani-rad, Ali Rahbari, Touradj Ebadzadeh, Microwave sintering of aluminum-ZrB2 composite: focusing on microstructure and mechanical properties, J. Mater. Res. 19 (4) (2016) 765e769. [37] Thelning, Karl-Erik. Steel and its heat treatment. Butterworth-Heinemann, 2013. Figure Caption
Fig. 1 Displacement, displacement rate and temperature vs sintering time of specimens: a) Fe, b) Fe-5wt%Al, c) Fe-5wt%Mo and d) Fe-5wt%Al-5wt%Mo.
Fig. 2 XRD patterns of heat treated samples (Fe-5Al and Fe-5Mo) and sintered samples (Fe-5Al, Fe-5Mo and Fe-5Al-5Mo)
Fig. 3 FESEM images of starting powders: a, b) Fe, c, d) Al and e, f) Mo
Fig. 4 Backscattered FESEM micrographs of sintered Fe sample
Fig. 5 FESEM images and elemental map analysis of Fe-5 wt% Al sample
Fig. 6 FESEM images and elemental map analysis of Fe-Al sample after heat treatment at 1100°C (annealed Fe-5 wt% Al)
Fig. 7 FESEM images and elemental MAP analysis of Fe-5Mo sample
Fig. 8 FESEM images and elemental map analysis of Fe-5 wt% Mo sample after heat treatment at 1100°C (annealed Fe-5 Mo)
Fig. 9 FESEM images and elemental map analysis of Fe-5 wt% Mo-5 wt% Al sample
Fig. 10 Schematic principle of the formation of FeMo intermetallic compounds during sintering process and post heat treatment
Fig. 11 Load-Extension curves of sintered and heat treated samples during bending strength test
Table 1 Physical and mechanical properties of sintered and heat treated iron alloys samples Relative density * Bending strength Microhardness (%) (MPa) (Vickers) Fe
99.8±0.1%
400±12
320±8
Fe-5Al
99.5±0.1%
510±17
386±23
Fe-5Al (anneal)
99.6±0.1%
480±10
350±25
Fe-5Mo
99.6±0.5%
621±21
572±42
Fe-5Mo (anneal)
99.6±0.5%
670±11
630±31
Fe-5Al-5Mo
99.7±0.2%
730±31
530±27
* Note: The amounts of interfacial products were not considered in the relative density calculation.