Abstract:
The structural properties of a magnetically semi-hard near equiatomic FeCo-2wt%V (FeCoV) alloy produced by Powder Injection Moulding (PIM) (option by fine metal powder - Metal Injection Moulding (MIM) technology) were investigated in this paper. Starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology was completed by high-temperature sintering for 3.5 hours at temperatures from 1370 to 1460 °C in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics.
The influence of sintering temperature was investigated concerning the aspects of the processes of structural transformation by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The appearance of an intense diffraction peak of the α'-FeCo phase (crystal structure type B2) was registered for all investigated samples. Structural parameters particle size Dmax, Feret X, and Feret Y exhibit constant increase with increase of sintering temperature.
Keywords: FeCoV alloy; MIM technology; Structural properties; Particle size Dmax; Feret X.
Сажетак: У раду су приказана истраживаъа структурних ceojemaea магнетнополутврде легуре FeCo-2wt%V (FeCoV) произведене технологи/ом бризгатьа композита праха са растопленим везивом (onyuja Opuseawa финих металних прахова - (MIM) mexnonoeuja). Почетни гранулат je припремлен мешаюъем FeCoV праха са везивом ниске вискозности. Након Opuzeara, зелени узорци су прво третирани растварачем, a затим термички са истим ци/ем уклаъаюъа везива. MIM mexnonoeuja je завршена високотемпературним синтероваъем y mpajarby 00 3,5 camu на температурама 00 1370 до 1460 °С y атмосфери водоника, yume cy obesbehene потребне магнетне и механичке карактеристике. Утица] температуре cunmepoeara на процес структурне трансформаци/е испитиван je методама рендгенске дифракци)е (XRD) и ckenupajyhe електронске mukpockonuje (SEM). За све испитиване узорке регистрована je nojasa интензивног дифракционог пика o'-FeCo кристалне фазе (структура типа B2). Структурни параметри величине честица Dmax, Feret X и Feret Y nokazyjy константно повейаъе ca noeehamem температуре cunmeposama до 1430 °C, док на вишим температурама долази до потпуног топльеъа синтерованих честица..
Къучне речи: FeCoV легура, MIM mexnonoeuja, структурна ceojemea, величина честице Dmax, Feret X.
1. Introduction
Magnetic alloys based on iron and cobalt are known for their exceptional combination of high values of magnetic induction of saturation and Curie temperature. Fig. 1 shows the correlation between high values of magnetic induction of saturation and high values of Curie temperature of commercial alloy VACOFLUX®50 based on iron and cobalt composition 49Fe49C02V (VACUUMSCHMELZE GmbH & Co. KG - Germany [1,2]). Most magnetically soft and magnetically semi-hard materials have Curie temperatures between 350 and 550 °C, while only VACOFLUX 50 alloy has a ferromagnetic-paramagnetic transition temperature of about 950 °C, which makes it extremely important because it is unique with this property.
At operating temperatures of about 700 °C, it retains high values of magnetic induction of saturation above 2 T, and at temperatures of about 800 °C values of magnetic induction of saturation are above 1.6 T. Amorphous magnetic soft alloys with relatively high values of magnetic permeability based on cobalt (VITROVAC 6150 Bs = 1 T; Тс = 480 °C) [3], or based on iron (VITROVAC 7505 Bs = 1.4 T; Tc = 420 °C) [4, 5], are not competitive for applications at extremely high operating temperatures.
Based on the technology of injection of powder composites with molten binder, efficient production of ceramic or metal parts with complex geometries has been achieved [612]. PIM technology is widely used for the production of components of magnetically soft and magnetically hard materials. There are ceramic CIM (Ceramic Injection Molding) magnets (eg ferrite) or metal MIM (Metal Injection Molding) magnets (eg alloys based on Fe, Co, or based on a combination of FeCo, as is the case with FeCoV alloy). The obtained alloy samples have functional properties that directly depend on the applied technological parameters. MIM manufactured parts with complex geometries and high saturation magnetization and high Curie temperature, making them useful for high-temperature and power-dense applications (e. g. aviation devices).
Alloys of FeCoV systems usually contain 45-55 wt.% Fe, 45-55 wt.% Co and 1.5-2.5 wt.% V. Increasing the vanadium content (4-7 wt.%) leads to excellent mechanical properties but significantly reduces the magnetic induction of Bs saturation. It is also possible to introduce titanium in a small percentage (0.4-1.4 wt.% Ti) instead of vanadium to achieve even better mechanical properties [13]. The 49Fe49C02V alloy is studied for its combination of good magnetic properties and improved mechanical and thermal properties compared to other alloys in the FeCoV system. Binary alloys of Fe - Co systems containing 33-55 wt.% Co are very brittle due to the formation of an ordered superlattice at temperatures below 730 °C. Addition of about 2 wt.% V prevents transformation into an ordered structure and enables a relatively high value of electrical resistivity (significantly higher values compared to other alloying elements, W, Ti, Mo, Mn, Ta, Cu, Ni,...ect.).
Using MIM technology, it is possible to obtain magnetically soft alloys of the FeCo system without the addition of vanadium at significantly lower sintering temperatures (of about 980 °C [14]) compared to standard sintering temperatures, which are usually in the range between 1300 and 1400 °C. However, alloys of the vanadium-free FeCo system cannot be used for many applications where high HV hardness values are necessary (V is an alloying element that provides very good mechanical and suitable electrical properties). Alloys of FeCoV system with equal participation of Fe and Co, and with 2-5 wt.% V also has a high electrical resistivity (due to the addition of vanadium), which significantly reduces losses due to eddy currents. It should be noted that iron-cobalt based amorphous alloys prepared by inrotating water melt-spinning technique exhibit high electrical resistivity accompanied by specific applications in sensorics [15].
In this study, we have characterized iron-cobalt based near equiatomic Fe49C049V2 alloy samples produced by MIM technology followed by the sintering process. Sintering was performed during 3.5 hours: from 1370 to 1460 °C, and structural features were investigated as a function of sintering temperature.
2. Materials and Experimental Procedures
Toroidal samples of 49Fe49C02V alloy were produced by MIM technology so the initial granulate was prepared by mixing FeCoV powder with a low-viscosity binder [16]. After injection (injection molding machine Battenfeld HM 600/130), the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. Finally, MIM technology is completed by high-temperature sintering that provides the necessary magnetic and mechanical characteristics [17-19]). Sintering was performed for 3.5 hours at temperatures from 1370 to 1460 °C in a hydrogen atmosphere. Crystallinity was investigated by XRD pattern (Philips PW 1050 diffractometer using Cu-K, radiation À = 0.154 nm and Bragg-Brentano focusing geometry with step/collection time scan mode of 0.05 °/s). Microstructural characterization was performed with a scanning electron microscope (SEM JEOL JSM-6390 LV).
3. Results and Discussion
The X-ray diffraction patterns of 49Fe49C02V alloy samples sintered from 1370 to 1460 °C are presented in Fig. 2. All patterns exhibit the main diffraction peak of a'-FeCo phase (crystal structure type B2), which increases with an increase of sintering temperature.
The microstructures of the 49Fe49Co2V alloy samples were investigated from the surfaces of the tested samples using scanning electron microscopy - SEM. Fig. 3. shows examples of microstructure sequences used to obtain quantitative parameters of stereological analysis of samples sintered at a) 1370 °C, b) 1400°C, and с) 1430 °C (the analysis included 3 sequences with about 120 samplings). From the presented microstructures, it can be first noticed that during sintering, powder particles were melted, which is directly proportional to the sintering temperature, i.e. at higher temperatures, neck growth and loss of particle individuality are more intense. The space between particles significantly changes shape due to pore closure, which leads to an increase in sample density (so-called intermediate sintering phase that takes place at 1370 °C, 1400 °C, and 1430 °C which is shown in Fig. 3. a,b,c respectively). In the final stage of sintering, at the highest temperature of 1460 °C, the particles completely lose their individuality due to melting (Fig. 3d), and the crystallization process is the most intensive.
Histograms of relative frequency and cumulative curve of distribution of Dmax, Feret X, and Feret Y particle size parameter values obtained by stereological analysis of 49Fe49C02V alloy sample sintered at 1370 °C are shown in Fig. 4, while Table I shows minimum, maximum, and mean values of monitored particle parameters of the same test sample. Most particles have a size of about 6 ит to 17 ит (mean value is about 12.4 ит), and for Feret X and Feret Y, the mean values are about 8.3 ит and 9.1 um, respectively.
Histograms of relative frequency and cumulative curve of distribution of Dmax, Feret X, and Feret Y particle size parameter values obtained by stereological analysis of 49Fe49Co2V alloy sample sintered at 1400 °C are shown in Fig. 5, while Table II shows minimum, maximum, and mean values of monitored particle parameters of the same test sample. Most particles have a size of about 7 ит to 18 ит (mean value is about 13.5 um), and for Feret X and Feret Y, the mean values are about 9.4 ит and 9.5 um, respectively.
About the results of the stereological analysis obtained with the sample sintered at 1370 °C, a slight increase in all three monitored parameters was observed after the increase of the sintering temperature by 30 °C. The choice of sintering temperatures was made with a gradual increase of only 30 °C in order to optimize the microstructures and therefore all other functional properties of the MIM technology synthesized samples of 49Fe49C02V alloy.
The histograms of the relative frequency and the cumulative curve of the distribution of the values of the particle size parameters Dmax, Feret X, and Feret Y obtained by stereological analysis of a sample of 49Fe49C02V alloy sintered at 1430 °C are shown in Fig. 6. Table Ш shows the minimum, maximum and mean values of the monitored particle parameters of the same sample. Most particles have a size of 10 ит to 20 ит (mean value is about 15 um), and for Feret X and Feret Y, mean values are about 10 um and 11 pm, respectively.
Concerning the results of the stereological analysis obtained with samples sintered at 1370 and 1400 °C, a further increase in all three monitored parameters was noticeable after a further increase in the sintering temperature. Table IV shows the comparative values of the monitored parameters (particle size Dmax, Feret X, and Feret Y) of all tested samples.
A comparison of the cumulative frequencies of the Feret X parameter of the 49Fe49C02V alloy samples sintered at 1370, 1400, and 1430 °C is shown in Fig. 8, and the cumulative frequencies of the Feret Y parameter are shown in Fig. 9.
From the comparative curves of cumulative frequencies of values of monitored parameters (particle size Dmax, Feret X, and Feret Y) of all tested samples, a constant and gradual increase of all three parameters with an increase in sintering temperature of 30 °C is noticeable. In this way, the microstructure of the samples sintered at 1370, 1400, and 1430 °C was gradually optimized, while the microstructure of the sample sintered at 1460 °C shows that the melting point of the particles was reached at this highest temperature. Experiments devoted to the hole-making method in 49Fe49C02V rod samples prepared by a vacuum агсmelting furnace and heat treated at 900 °C show the microstructure that contains a dual phase of BCC and B2 with the matrix grain size of about 40-50 pm [20]. Therefore, MIM technology offers the successful preparation of intermetallic FeCoV components that can be used competitively in strategic applications, for example, the aerospace motor rotor.
4. Conclusion
On the microstructures of 49Fe49Co2V alloy samples examined using a scanning electron microscope - SEM, it can be noticed that during sintering, powder particles are melted directly in proportion to the sintering temperature. At higher temperatures, neck growth and loss of particle individuality are more intense, and the space between particles significantly changes shape due to pore closure. This leads to an increase in sample density (so-called intermediate sintering phase that takes place at 1370, 1400, and 1430 °C). The values of monitored parameters (particle size Dmax, Feret X, and Feret Y) of tested samples exhibit a constant and gradual increase with increasing sintering temperature. In the final stage of sintering, at the highest temperature of 1460 °C, the particles completely lose their individuality due to melting.
Acknowledgments
This work is partially funded by the Ministry of Science, Technological Development and Innovations of the Republic of Serbia (project no. 451-03-47/2023-14/200132, Faculty of Technical Sciences in Cacak, University of Kragujevac).
ORCID numbers:
Borivoje Nedeljkovic, https://orcid.org/0000-0003-4923-3174
Vladimir В. Pavlovié, https://orcid.org/0000-0002-1 138-0331
Nina Obradovic, https://orcid.org/0000-0002-7993-293X
Nebojsa Mitrovic, https://orcid.org/0000-0002-7971-6321
© 2024 Authors. Published by association for ETRAN Society. This article is an open access article distributed under the terms and conditions of the Creative Commons - Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0/).
5. References
1. Soft Magnetic Cobalt-Iron Alloys (vacuumschmelze.com)
2. PB-PHT-001 e neu (vacuumschmelze.com)
3. M. Kurniawan, V. Keylin, and M. E. McHenry, "Alloy substituents for cost reduction in soft magnetic materials", Journal of Materials Research, vol. 30, pp. 1072-1077, 2015.
4. A. Makino, K. Suzuki, A. Inoue, and T. Masumoto, "Nanocrystalline soft magnetic Fe-MВ (M=Zr, Hf, №) alloys produced by crystallization of amorphous phase", Mater. Trans. JIM, vol. 36, pp. 924-938, 1995.
5. M. E. McHenry, M. A. Willard, D. E. Laughlin, "Amorphous and nanocrystalline materials for applications as soft magnets", Progress in Materials Science, vol. 44 (1999) 291-433.
6. T. Sourmail, "Near equiatomic FeCo alloys: Constitution, mechanical and magnetic properties", Progress in Materials Science, 50 (2005) 816-880.
7. N. H. Loh, $. В. Tor, К. A. Khor, "Production of metal matrix composite part by powder injection molding", Journal of Materials Processing Technology, vol. 108 (2001) 398- 407.
8. В. Zlatkov, N. Mitrovic, M-V. Nikolié, A. Maricic, H. Danninger, O. Aleksic, Е. Halwax, "Properties of MnZn ferrites prepared by powder injection molding technology", Materials Science and Engineering B-Advanced Functional Solid-state Materials, vol. 175 (2010) 217-222.
9. Н. Shokrollahi, К. Janghorban, "Soft magnetic composite materials (SMCs)", Journal of Materials Processing Technology, vol. 189 (2007) 1-12.
10. P. Setasuwon, A. Bunchavimonchet, S. Danchaivijit, "The effects of binder components in wax/oil systems for metal injection molding", Journal of Materials Processing Technology, vol. 196 (2008) 94-100.
11. H. Ye, X. Y. Liu, H. Hong, "Fabrication of metal matrix composites by metal injection molding-A review", Journal of Materials Processing Technology, vol. 200, (2008) 12-24.
12. K. Samet, M. Subasi, C. Karatas, "The effect of insert surface roughness in part production with inserted powder injection molding method", Science of Sintering, vol. 55 (2023) 89-101.
13. C. W. Chen, "Magnetism and metallurgy of soft magnetic materials", Amsterdam, Nort Holland Publishing Company, 1977.
14. A. Silva, J. A. Lozano, R. Machado, J. A. Escobar, P. A.P. Wendhausen, "Study of soft magnetic iron cobalt based alloys processed by powder injection molding", Journal of Magnetism and Magnetic Materials, vol. 320 (2008) 393-396.
15. J. М. Orelj, N. S. Mitrovic, У. В. Pavlovié, "MI-sensor element features and estimation of penetration depth and magnetic permeability by magnetoresistance and magnetoreactance of CoFeSiB amorphous wires", IEEE Sensors Journal, vol. 23 (2023) 14017-14024.
16. В. Nedeljkovic, N. Mitrovic, J. Orelj, N. Obradovi , У. Pavlovi , "Characterization of FeCoV alloy processed by PIM/MIM route", Science of Sintering, vol. 49 (2017) 299- 309.
17. А. Behvandi, H. Shokrollahi, В. Chitsazan, М. Ghaffari, "Magnetic and structural studies of mechanically alloyed nano-structured Fe49C049V2 powder", Journal of Magnetism and Magnetic Materials, vol. 322 (2010) 3932-3937.
18. B. Chitsazan, H. Shokrollahi, A. Behvandi, M. Ghaffari, "Magnetic, structural and micro-structural properties of mechanically alloyed nano-structured FessCo4sVs powder containing inter-metallic Co3V", Journal of Magnetism and Magnetic Materials, vol. 323 (2011) 1128-1133.
19. В. Weidenfeller, M. Anhalt, W. Riehemann, "Variation of magnetic properties of composites filled with soft magnetic FeCoV particles by particle alignment in a magnetic field", Journal of Magnetism and Magnetic Materials, vol. 320 (2008) 362-365.
20. Y. Zhang, К. Kang, Z. Dong, О. Wang, X. Zhu, К. Xu, D. Guo, "Microstructural evolution of soft magnetic 49Fe-49C0-2V alloy induced by drilling", Materials & Design, vol. 189 (2020) 108501.
*) Corresponding author: [email protected] (Dr. Nebojša Mitrović)
You have requested "on-the-fly" machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Show full disclaimer
Neither ProQuest nor its licensors make any representations or warranties with respect to the translations. The translations are automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. PROQUEST AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the translations is subject to all use restrictions contained in your Electronic Products License Agreement and by using the translation functionality you agree to forgo any and all claims against ProQuest or its licensors for your use of the translation functionality and any output derived there from. Hide full disclaimer
© 2024. This work is published under https://creativecommons.org/licenses/by/4.0/ (the "License"). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.
Abstract
The structural properties of a magnetically semi-hard near equiatomic FeCo-2wt%V (FeCoV) alloy produced by Powder Injection Moulding (PIM) (option by fine metal powder - Metal Injection Moulding (MIM) technology) were investigated in this paper. Starting granulate was prepared by mixing FeCoV powder with a low-viscosity binder. After injection, the green samples were first treated with a solvent and then thermally with the same aim of removing the binder. MIM technology was completed by high-temperature sintering for 3.5 hours at temperatures from 1370 to 1460 °C in a hydrogen atmosphere, which provides the necessary magnetic and mechanical characteristics. The influence of sintering temperature was investigated concerning the aspects of the processes of structural transformation by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The appearance of an intense diffraction peak of the α'-FeCo phase (crystal structure type B2) was registered for all investigated samples. Structural parameters particle size Dmax, Feret X, and Feret Y exhibit constant increase with increase of sintering temperature.