Journal of Materials Science

, Volume 52, Issue 22, pp 13284–13295 | Cite as

Enhancement in the elongation, yield strength and magnetic properties of intermetallic FeCo alloy using spark plasma sintering

  • Amar J. AlbaajiEmail author
  • Elinor G. Castle
  • Mike J. Reece
  • Jeremy P. Hall
  • Sam L. Evans


Equiatomic FeCo alloys were densified using spark plasma sintering (SPS). Using a constant 50 MPa pressure, the sintering temperature and dwell times for the SPS process were optimised for different heating rates (50, 100, 300 °C min−1). All samples used in this optimisation process were analysed in terms of their mechanical and magnetic properties. Interestingly, for all heating rates, FeCo samples sintered at the highest temperatures (1100 °C) without dwelling exhibited an increased tensile yield strength combined with an improvement in the elongation to fracture. This occurred despite the microstructural coarsening observed at this sintering temperature, which decreased the ultimate tensile strength. Improved grain boundary bonding in the samples sintered at the highest sintering temperature led to a suppression of intergranular fracture, something previously considered to be inherent to all equiatomic FeCo alloy structures. An optimum combination of mechanical (ultimate tensile strength = 400 MPa, yield strength = 340 MPa and strain to failure = 3.5%) and magnetic (saturation induction (B sat) of 2.39 T and coercivity (Hc) of 612 A m−1) properties was achieved by sintering to 1100 °C using a relatively slow heating rate of 50 °C min−1 with no dwell time.


  1. 1.
    Sundar RS, Deevi SC (2005) Soft magnetic FeCo alloys: alloy development, processing, and properties. Int Mater Rev 50(3):157–192. doi: 10.1179/174328005x14339 CrossRefGoogle Scholar
  2. 2.
    Sourmail T (2005) Near equiatomic FeCo alloys: constitution, mechanical and magnetic properties. Prog Mater Sci 50(7):816–880. doi: 10.1016/j.pmatsci.2005.04.001 CrossRefGoogle Scholar
  3. 3.
    Zhao L, Baker I, George EP (1993) Room temperature fracture of FeCo. In: Materials research society symposium proceedings, vol 288. doi: 10.1557/PROC-288-501
  4. 4.
    Zhao L, Baker I (1994) The effect of grain size and Fe: Co ratio on the room temperature yielding of FeCo. Acta Metall Mater 42(6):1953–1958. doi: 10.1016/0956-7151(94)90020-5 CrossRefGoogle Scholar
  5. 5.
    Jordan KR, Stoloff NS (1969) Plastic deformation and fracture in FeCo-2%V. Trans Metal Soc AIME 245:2027–2034Google Scholar
  6. 6.
    Sundar R, Deevi S (2004) Influence of alloying elements on the mechanical properties of FeCo–V alloys. Intermetallics 12:7–9. doi: 10.1016/j.intermet.2004.02.022 Google Scholar
  7. 7.
    Chen CW (1961) Metallurgy and magnetic properties of an Fe–Co–V Alloy. J Appl Phys 32(3):S348–S355. doi: 10.1063/1.2000465 CrossRefGoogle Scholar
  8. 8.
    Kawahara K (1983) Effect of carbon on mechanical properties in Fe0.5 Co0.5 alloys. J Mater Sci 18:2047–2055. doi: 10.1007/BF00554997 CrossRefGoogle Scholar
  9. 9.
    George E, Gubbi AN, Baker I, Robertson L (2002) Mechanical properties of soft magnetic FeCo alloys. Mater Sci Eng A 329–331:325–333. doi: 10.1016/S0921-5093(01)01594-5 CrossRefGoogle Scholar
  10. 10.
    Thornburg DR (1969) High-strength high-ductility Cobalt–Iron alloys. J Appl Phys 40(3):1579–1580. doi: 10.1063/1.1657779 CrossRefGoogle Scholar
  11. 11.
    Pitt CD, Rawlings RD (1983) Lüders strain and ductility of ordered Fe–Co–2V and Fe–Co–V–Ni alloys. Met Sci 17(6):261–266. doi: 10.1179/030634583790420835 CrossRefGoogle Scholar
  12. 12.
    Sundar RS, Deevi SC (2004) Effect of heat-treatment on the room temperature ductility of an ordered intermetallic Fe–Co–V alloy. Mater Sci Eng A 369:1–2. doi: 10.1016/j.msea.2003.11.004 CrossRefGoogle Scholar
  13. 13.
    Sundar RS, Deevi SC, Reddy BV (2005) High strength FeCo–V intermetallic alloy: electrical and magnetic properties. J Mater Res 20(6):1515–1522CrossRefGoogle Scholar
  14. 14.
    Fingers RT (1998) Creep behavior of thin laminates of FeCo alloys for use in switched reluctance motors and generators. Ph.D. thesis, Virginia Polytechnic InstituteGoogle Scholar
  15. 15.
    Rutz HG, Hanejko FG, Ellis GW, Riverton NJ (1997) The manufacture of electromagnetic components by the powder metallurgy process. In: International conference on powder metallurgy and particulate materials, June 29–July 2, Chicago, IL USA, 1Google Scholar
  16. 16.
    Munir ZA, Anselmi-Tamburini U, Ohyanagi M (2006) The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method. J Mater Sci 41(3):763–777. doi: 10.1007/s10853-006-6555-2 CrossRefGoogle Scholar
  17. 17.
    Mamedov V (2002) Spark plasma sintering as advanced PM sintering method. Powder Metall 45(4):322–328. doi: 10.1179/003258902225007041 CrossRefGoogle Scholar
  18. 18.
    Silva A, Wendhausen P, Machado R, Ristow W (2007) Magnetic properties obtained for Fe-50Co alloy produced by MIM with elemental powders. Mater Sci Forum 534–536:1353–1356. doi: 10.4028/ CrossRefGoogle Scholar
  19. 19.
    Sun Y, Haley J, Kulkarni K, Aindow M, Lavernia EJ (2015) Influence of electric current on microstructure evolution in Ti/Al and Ti/TiAl 3 during spark plasma sintering. J Alloys Compd 648:1097–1103. doi: 10.1016/j.jallcom.2015.07.079 CrossRefGoogle Scholar
  20. 20.
    Sun Y, Kulkarni K, Sachdev AK, Lavernia EJ (2014) Synthesis of γ-TiAl by reactive spark plasma sintering of cryomilled Ti and Al powder blend, part I: influence of processing and microstructural evolution. Metall Mater Trans A 45(6):2750–2758. doi: 10.1007/s11661-014-2215-3 CrossRefGoogle Scholar
  21. 21.
    Kulkarni KN, Sun Y, Sachdev AK, Lavernia E (2013) Field-activated sintering of blended elemental γ-TiAl powder compacts: porosity analysis and growth kinetics of Al 3 Ti. Scr Mater 68(11):841–844. doi: 10.1016/j.scriptamat.2013.02.004 CrossRefGoogle Scholar
  22. 22.
    Mani MK, Viola G, Reece MJ, Hall JP, Evans SL (2013) Structural and magnetic characterization of spark plasma sintered Fe-50Co alloys. In: MRS proceedings, vol 1516. doi: 10.1557/opl.2012.1669
  23. 23.
    Räthel J, Herrmann M, Beckert W (2009) Temperature distribution for electrically conductive and non-conductive materials during Field Assisted Sintering (FAST). J Eur Ceram Soc 29(8):1419–1425. doi: 10.1016/j.jeurceramsoc.2008.09.015 CrossRefGoogle Scholar
  24. 24.
    Dieter George E (1986) Mechanical metallurgy, 3rd edn. McGraw-Hill, New YorkGoogle Scholar
  25. 25.
    Roura P, Costa J, Farjas J (2002) Is sintering enhanced under non-isothermal conditions? Mater Sci Eng A 337(1):248–253. doi: 10.1016/S0921-5093(02)00029-1 CrossRefGoogle Scholar
  26. 26.
    Hungría T, Galy J, Castro A (2009) Spark plasma sintering as a useful technique to the nanostructuration of piezo-ferroelectric materials. Adv Eng Mater 11(8):615–631. doi: 10.1002/adem.200900052 CrossRefGoogle Scholar
  27. 27.
    Hu K, Li X, Qu S, Li Y (2013) Effect of heating rate on densification and grain growth during spark plasma sintering of 93W–5.6 Ni–1.4 Fe heavy alloys. Metall Mater Trans A 44(9):4323–4336. doi: 10.1007/s11661-013-1789-5 CrossRefGoogle Scholar
  28. 28.
    Guillon O, Gonzalez-Julian J, Dargatz B, Kessel T, Schierning G, Räthel J, Herrmann M (2014) Field-assisted sintering technology/spark plasma sintering: mechanisms, materials, and technology developments. Adv Eng Mater 16(7):830–849. doi: 10.1002/adem.201300409 CrossRefGoogle Scholar
  29. 29.
    Albaaji AJ, Castle EG, Reece MJ, Hall JP, Evans SL (2016) Mechanical and magnetic properties of spark plasma sintered soft magnetic FeCo alloy reinforced by carbon nanotubes. J Mater Res 31(21):3448–3458. doi: 10.1557/jmr.2016.372 CrossRefGoogle Scholar
  30. 30.
    Munir ZA, Quach DV, Ohyanagi M (2011) Electric current activation of sintering: a review of the pulsed electric current sintering process. J Am Ceram Soc 94(1):1–19. doi: 10.1111/j.1551-2916.2010.04210.x CrossRefGoogle Scholar
  31. 31.
    Krein R, Friak M, Neugebauer J, Palm M, Heilmaier M (2010) L2 1-ordered Fe–Al–Ti alloys. Intermetallics 18(7):1360–1364. doi: 10.1016/j.intermet.2009.12.036 CrossRefGoogle Scholar
  32. 32.
    Baker I, Schulson EM (1989) On grain boundary disorder and the tensile ductility of polycrystalline ordered alloys: a hypothesis. Scr Metall 23(3):345–348. doi: 10.1016/0036-9748(89)90379-7 CrossRefGoogle Scholar
  33. 33.
    Albaaji AJ, Castle EG, Reece MJ, Hall JP, Evans SL (2016) Synthesis and properties of graphene and graphene/carbon nanotube-reinforced soft magnetic FeCo alloy composites by spark plasma sintering. J Mater Sci 51(16):7624–7635. doi: 10.1007/s10853-016-0041-2 CrossRefGoogle Scholar
  34. 34.
    Schulson EM, Barker DR (1983) A brittle to ductile transition in NiAl of a critical grain size. Scr Metall 17(4):519–522. doi: 10.1016/0036-9748(83)90344-7 CrossRefGoogle Scholar
  35. 35.
    Clegg DW, Buckley RA (1973) The disorder → order transformation in Iron–Cobalt-based alloys. Met Sci 7(1):48–54. doi: 10.1179/030634573790445541 CrossRefGoogle Scholar
  36. 36.
    Stoloff NS, Davies RG (1964) The plastic deformation of ordered FeCo and Fe3Al alloys. Acta Metall 12:473–485. doi: 10.1016/0001-6160(64)90019-7 CrossRefGoogle Scholar
  37. 37.
    Liu CT, Stiegler JO (1984) Ductile ordered intermetallic alloys. Science 226:636–643CrossRefGoogle Scholar
  38. 38.
    Xie G, Ohashi O, Yoshioka T, Song M, Mitsuishi K, Yasuda H, Furuya K, Noda T (2001) Effect of interface behavior between particles on properties of pure Al powder compacts by spark plasma sintering. Mater Trans 42(9):1846–1849. doi: 10.2320/matertrans.42.1846 CrossRefGoogle Scholar
  39. 39.
    Randall M (1996) German sintering theory and practice. Wiley, New YorkGoogle Scholar
  40. 40.
    Zhang Zhao-Hui, Wang Fu-Chi, Lin Wang S-KL (2008) Ultrafine-grained copper prepared by spark plasma sintering process. Mater Sci Eng A 476:1–2. doi: 10.1016/j.msea.2007.04.107 CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  1. 1.Wolfson Centre for Magnetics, Cardiff School of EngineeringCardiff UniversityCardiffUK
  2. 2.College of EngineeringThe University of Al-QadisiyahAl DiwaniyahIraq
  3. 3.School of Engineering and Materials ScienceQueen Mary University of LondonLondonUK
  4. 4.Nanoforce Technology Ltd.LondonUK
  5. 5.Institute of Mechanical and Manufacturing Engineering, Cardiff School of EngineeringCardiff UniversityCardiffUK

Personalised recommendations