- Email: [email protected]
Glass forming abilities and magnetic properties of soft magnetic Fe–Co–Zr–W–B bulk glassy alloys
ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735 www.elsevier.com/locate/jmmm
Glass forming abilities and magnetic properties of soft magnetic Fe–Co–Zr–W–B bulk glassy alloys Piotr Pawlika,, Katarzyna Pawlika, Hywel A. Daviesb, Jerzy J. Wys"ockia, Waldemar Kaszuwarac, Marcin Leonowiczc a Institute of Physics, Cze¸stochowa University of Technology, Al. Armii Krajowej 19, 42-200 Cze¸stochowa, Poland Department of Engineering Materials, Center for Advanced Magnetic Materials and Devices, The University of Sheffield, Sheffield, S1 3JD, UK c Department of Engineering Materials, Nanocenter, Warsaw University of Technology, ul. Wo!oska 141, Warsaw, Poland
b
Available online 20 March 2006
Abstract Melt-spun ribbon samples of various thicknesses up to 350 mm and suction-cast 1 and 2 mm diameter rods of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys, were produced. The results obtained for rods indicate relatively large saturation polarization Js , with high anisotropy field that lowers the permeability of the samples. X-ray diffractometry was applied to confirm the amorphous structure of the processed alloys. r 2006 Elsevier B.V. All rights reserved. PACS: 75.50 Kj; 75.60 Ej; 76.80+y Keywords: Fe-based bulk glassy alloys; Soft magnetic materials; Glass forming ability
1. Introduction Iron-based bulk glassy alloys are particularly interesting due to their soft magnetic properties and thus their potential magnetic applications. The maximum diameter of fully amorphous rods was reported to reach 6 mm for an Fe61 Co7 Zr10 Mo5 W2 B15 alloy [1]. However, the alloy is paramagnetic in the amorphous state at room temperature, as a consequence of the large fractions of metalloid and refractory metal elements and this limits any potential applications for this alloy. Much better magnetic properties were reported for Fe–Ga–Cr–Mo–P–B–C-type alloys, but the maximum diameter of fully amorphous rods for alloys of this type was limited to 1 mm [2]. Other interesting compositions were reported by Chiriac and Lupu in Ref. [3], for which relatively low values of the eddy current losses were measured for toroidal bulk amorphous samples of compositions (Fe, Co, Ni)70 (Zr, Nb, M)10 B20 (M ¼ Zr, Ti, Ta, Mo). In this work, the results of an investigation of the magnetic properties and thermal stability of novel Corresponding author. Tel./fax: +48 0 34 325 07 95.
E-mail address: [email protected] (P. Pawlik). 0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2006.02.206
Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys, having good glass forming abilities, are presented. 2. Samples preparation and investigation methods Samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys were produced by arc-melting under an Ar atmosphere high-purity elemental Fe, Co, W and Zr and pre-alloyed Fe–B of known, chemically analyzed composition. From this alloy precursor, ribbon samples of various thicknesses up to 350 mm were produced by melt-spinning in a controlled atmosphere. The ribbon thickness was varied by changing the speed of the copper roll. Rod and tube samples of various diameters were produced by suctioncasting of the melt into a split copper die, using an argon pressure difference between two chambers integrated within the arc-melting unit. X-ray diffraction with CoKa radiation and Mo¨ssbauer spectroscopy were used for the assessment of the ribbon and rod samples microstructure. Magnetic properties of the rod samples were measured by LakeShore VSM magnetometer operating in an external magnetic field up to 2 T.
ARTICLE IN PRESS P. Pawlik et al. / Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735
e734
The glass transition temperature T g , crystallization temperature T x , melting temperature T m and reduced glass transition temperature T rg ¼ T g =T m were determined from the DTA and DSC traces for the samples measured in the temperature range 300–1470 K and DSC (300–973 K), under Ar atmosphere.
3. Results and discussion X-ray diffraction patterns recorded for melt-spun ribbon samples of various thicknesses, indicated the approximal maximum thickness of fully amorphous ribbons for a particular alloy. The largest thickness of ribbon samples was measured for the x ¼ 0 alloy (Fig. 1a). Specimens not thicker than 220 mm were fully amorphous, while thicker ribbons contained some crystalline phases within an amorphous matrix. The maximum thickness of fully amorphous sample for unidirectionally cooled ribbon indicated good glass forming ability for the investigated alloy, which suggested that bulk glassy samples of large
dimensions could be cast. A decrease of the maximum thickness of fully amorphous ribbon was observed with decreasing W content down to 170 mm for the x ¼ 2 alloy and 140 mm for the x ¼ 3 alloy. Microstructural investigation of the bulk samples revealed that the rods were fully amorphous up to a diameter of 2 mm for the x ¼ 0 alloy. A similar decrease of the maximum, fully glassy rod diameter with decreasing W was observed as for the ribbon samples; thus fully amorphous rods of diameter 1 and 0.5 mm were produced for the x ¼ 2 and 3 alloys, respectively. Differential scanning calorimetry was performed on the fully amorphous ribbon samples for all three compositions investigated to determine their thermal stability parameters. A two-stage crystallization process was observed for all three alloys (Fig. 2). Gradual decrease of the glass transition temperature T g from 834 K (for 4 at% of W) to 807 K (for 1 at% of W), and both crystallization temperatures T x1 , T x2 from T x1 ¼ 875 K (for 4 at% of W) to 850 K (for 1 at% of W) and from T x2 ¼ 1058 K (for 4 at% of W) to 965 K (for 1 at% of W) were observed, with decreasing W, while almost constant values of the melting temperature T m 1380 K were measured. The reduced glass
d=180-350 µm 40 Tx1
20
d=110-220 µm
Tm Tx2
0 d=40-66 µm
Tg
-20
30
40
50 60 Angle, 2Θ[deg]
(a)
70
40
80
400
600
800
1000
1200
1400 Tm
Tx1 ∆ [K]
Lineintensities [a.u.]
Fe61Co10Zr5W4B20
Tx2
20 Tg 0
rod-φ=2mm
Fe61Co12Zr5W2B20
-20 400
600
800
1200
1400
Tx1
10
rod-φ=1mm
1000
Tg
Tm
Tx2
0 Fe61Co13Zr5W1B20 -10 30 (b)
40
50
60
70 80 90 Angle, 2Θ[deg]
100
110
120
Fig. 1. XRD scans for the Fe61 Co10 Zr5 W4 B20 alloy as-cast ribbon samples of various thicknesses (a) and suction-cast rods of the diameter 1 and 2 mm (b).
400
600
800 1000 Temperature,T[K]
1200
1400
Fig. 2. DTA scans measured for amorphous ribbon samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys (10 K/min under Ar atmosphere).
ARTICLE IN PRESS P. Pawlik et al. / Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735
1.0
M(T)/Mmax
Fe and B elements. This type of hyperfine field distribution suggests the occurrence of spinodal decomposition of the amorphous phase. Nevertheless, the broadening of the Mo¨ssbauer spectrum confirm the existence of an amorphous structure in the alloy.
Fe61Co13Zr5W1B20 Fe61Co12Zr5W2B20 Fe61Co10Zr5W4B20
0.8
e735
0.6
4. Conclusions
0.4 0.2 0.0 300
400
500 600 Temperature,T[K]
700
800
Fig. 3. Temperature dependence of the reduced magnetic moment measured for the amorphous ribbon samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys.
transition temperature T rg ¼ T g =T m decreases from 0.6 for the x ¼ 0 alloy to 0.58 for the x ¼ 3 alloy. Measurements of the hysteresis loops for the rod samples of the Fe61 Co10 Zr5 W4 B20 alloy indicated a low value of coercivity of 2 A=m and a high value of the anisotropy field 4000 A/m which reduces the permeability of the alloy [4]. As one can expect, on increasing the Co content from 10 to 12 at%, a significant rise of the Curie temperature T C was observed; however a further increase of Co contents to 13 at% does not change T C (Fig. 3). A similar behavior of the saturation polarization with Co content was observed. Mo¨ssbauer spectroscopy measurements, carried out on 1 mm as-cast rod samples were reported by Pawlik et al. [5]. They revealed, typically for the amorphous alloys a broadening of the Mo¨ssbauer lines. The hyperfine field distribution obtained from the Mo¨ssbauer spectrum analysis consists of low- and high-field components, which suggests the coexistence of two amorphous constituent phases. In these phases, the first neighborshell surrounding the Fe atoms may contain various volume fractions of Co,
Investigation of novel Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys ribbon and rod samples produced by two rapid solidification processes, revealed remarkably good glass forming abilities together with good soft magnetic properties for the alloys. An decrease of W content results in significant shift of T g and T x down to the lower temperatures, while T m remains constant; thus leading to the decrease of T g =T m . At the same time, the decrease of maximum thickness of fully amorphous samples with decrease of W contents was observed, so that fully amorphous 220 mm thick melt-spun ribbon samples and 2 mm diameter suction-cast rods were produced for the x ¼ 0 alloy. Acknowledgment This research was supported by Polish Scientific Research Committee (KBN) (project nos. 3T08A 046 27 and 3T08A028 25). References [1] A. Inoue, T. Zhang, A. Tekeuchi, Appl. Phys. Lett. 71 (1997) 464. [2] M. Stoica, J. Eckert, S. Roth, L. Schultz, Mater. Sci. Eng. A 375–377 (2004) 399. [3] H. Chiriac, N. Lupu, Mater. Sci. Eng. A 375–377 (2004) 255. [4] P. Pawlik, H.A. Davies, M.R.J. Gibbs, Appl. Phys. Lett. 83 (2003) 2775. ˙ ak, J. Zbroszczyk, J.J. Wys"ocki, [5] P. Pawlik, M. Nabia"ek, E. Z J. Olszewski, K. Pawlik, Arch. Nauki Mat. 25 (2004) 177.
Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735 www.elsevier.com/locate/jmmm
Glass forming abilities and magnetic properties of soft magnetic Fe–Co–Zr–W–B bulk glassy alloys Piotr Pawlika,, Katarzyna Pawlika, Hywel A. Daviesb, Jerzy J. Wys"ockia, Waldemar Kaszuwarac, Marcin Leonowiczc a Institute of Physics, Cze¸stochowa University of Technology, Al. Armii Krajowej 19, 42-200 Cze¸stochowa, Poland Department of Engineering Materials, Center for Advanced Magnetic Materials and Devices, The University of Sheffield, Sheffield, S1 3JD, UK c Department of Engineering Materials, Nanocenter, Warsaw University of Technology, ul. Wo!oska 141, Warsaw, Poland
b
Available online 20 March 2006
Abstract Melt-spun ribbon samples of various thicknesses up to 350 mm and suction-cast 1 and 2 mm diameter rods of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys, were produced. The results obtained for rods indicate relatively large saturation polarization Js , with high anisotropy field that lowers the permeability of the samples. X-ray diffractometry was applied to confirm the amorphous structure of the processed alloys. r 2006 Elsevier B.V. All rights reserved. PACS: 75.50 Kj; 75.60 Ej; 76.80+y Keywords: Fe-based bulk glassy alloys; Soft magnetic materials; Glass forming ability
1. Introduction Iron-based bulk glassy alloys are particularly interesting due to their soft magnetic properties and thus their potential magnetic applications. The maximum diameter of fully amorphous rods was reported to reach 6 mm for an Fe61 Co7 Zr10 Mo5 W2 B15 alloy [1]. However, the alloy is paramagnetic in the amorphous state at room temperature, as a consequence of the large fractions of metalloid and refractory metal elements and this limits any potential applications for this alloy. Much better magnetic properties were reported for Fe–Ga–Cr–Mo–P–B–C-type alloys, but the maximum diameter of fully amorphous rods for alloys of this type was limited to 1 mm [2]. Other interesting compositions were reported by Chiriac and Lupu in Ref. [3], for which relatively low values of the eddy current losses were measured for toroidal bulk amorphous samples of compositions (Fe, Co, Ni)70 (Zr, Nb, M)10 B20 (M ¼ Zr, Ti, Ta, Mo). In this work, the results of an investigation of the magnetic properties and thermal stability of novel Corresponding author. Tel./fax: +48 0 34 325 07 95.
E-mail address: [email protected] (P. Pawlik). 0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2006.02.206
Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys, having good glass forming abilities, are presented. 2. Samples preparation and investigation methods Samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys were produced by arc-melting under an Ar atmosphere high-purity elemental Fe, Co, W and Zr and pre-alloyed Fe–B of known, chemically analyzed composition. From this alloy precursor, ribbon samples of various thicknesses up to 350 mm were produced by melt-spinning in a controlled atmosphere. The ribbon thickness was varied by changing the speed of the copper roll. Rod and tube samples of various diameters were produced by suctioncasting of the melt into a split copper die, using an argon pressure difference between two chambers integrated within the arc-melting unit. X-ray diffraction with CoKa radiation and Mo¨ssbauer spectroscopy were used for the assessment of the ribbon and rod samples microstructure. Magnetic properties of the rod samples were measured by LakeShore VSM magnetometer operating in an external magnetic field up to 2 T.
ARTICLE IN PRESS P. Pawlik et al. / Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735
e734
The glass transition temperature T g , crystallization temperature T x , melting temperature T m and reduced glass transition temperature T rg ¼ T g =T m were determined from the DTA and DSC traces for the samples measured in the temperature range 300–1470 K and DSC (300–973 K), under Ar atmosphere.
3. Results and discussion X-ray diffraction patterns recorded for melt-spun ribbon samples of various thicknesses, indicated the approximal maximum thickness of fully amorphous ribbons for a particular alloy. The largest thickness of ribbon samples was measured for the x ¼ 0 alloy (Fig. 1a). Specimens not thicker than 220 mm were fully amorphous, while thicker ribbons contained some crystalline phases within an amorphous matrix. The maximum thickness of fully amorphous sample for unidirectionally cooled ribbon indicated good glass forming ability for the investigated alloy, which suggested that bulk glassy samples of large
dimensions could be cast. A decrease of the maximum thickness of fully amorphous ribbon was observed with decreasing W content down to 170 mm for the x ¼ 2 alloy and 140 mm for the x ¼ 3 alloy. Microstructural investigation of the bulk samples revealed that the rods were fully amorphous up to a diameter of 2 mm for the x ¼ 0 alloy. A similar decrease of the maximum, fully glassy rod diameter with decreasing W was observed as for the ribbon samples; thus fully amorphous rods of diameter 1 and 0.5 mm were produced for the x ¼ 2 and 3 alloys, respectively. Differential scanning calorimetry was performed on the fully amorphous ribbon samples for all three compositions investigated to determine their thermal stability parameters. A two-stage crystallization process was observed for all three alloys (Fig. 2). Gradual decrease of the glass transition temperature T g from 834 K (for 4 at% of W) to 807 K (for 1 at% of W), and both crystallization temperatures T x1 , T x2 from T x1 ¼ 875 K (for 4 at% of W) to 850 K (for 1 at% of W) and from T x2 ¼ 1058 K (for 4 at% of W) to 965 K (for 1 at% of W) were observed, with decreasing W, while almost constant values of the melting temperature T m 1380 K were measured. The reduced glass
d=180-350 µm 40 Tx1
20
d=110-220 µm
Tm Tx2
0 d=40-66 µm
Tg
-20
30
40
50 60 Angle, 2Θ[deg]
(a)
70
40
80
400
600
800
1000
1200
1400 Tm
Tx1 ∆ [K]
Lineintensities [a.u.]
Fe61Co10Zr5W4B20
Tx2
20 Tg 0
rod-φ=2mm
Fe61Co12Zr5W2B20
-20 400
600
800
1200
1400
Tx1
10
rod-φ=1mm
1000
Tg
Tm
Tx2
0 Fe61Co13Zr5W1B20 -10 30 (b)
40
50
60
70 80 90 Angle, 2Θ[deg]
100
110
120
Fig. 1. XRD scans for the Fe61 Co10 Zr5 W4 B20 alloy as-cast ribbon samples of various thicknesses (a) and suction-cast rods of the diameter 1 and 2 mm (b).
400
600
800 1000 Temperature,T[K]
1200
1400
Fig. 2. DTA scans measured for amorphous ribbon samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys (10 K/min under Ar atmosphere).
ARTICLE IN PRESS P. Pawlik et al. / Journal of Magnetism and Magnetic Materials 304 (2006) e733–e735
1.0
M(T)/Mmax
Fe and B elements. This type of hyperfine field distribution suggests the occurrence of spinodal decomposition of the amorphous phase. Nevertheless, the broadening of the Mo¨ssbauer spectrum confirm the existence of an amorphous structure in the alloy.
Fe61Co13Zr5W1B20 Fe61Co12Zr5W2B20 Fe61Co10Zr5W4B20
0.8
e735
0.6
4. Conclusions
0.4 0.2 0.0 300
400
500 600 Temperature,T[K]
700
800
Fig. 3. Temperature dependence of the reduced magnetic moment measured for the amorphous ribbon samples of Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys.
transition temperature T rg ¼ T g =T m decreases from 0.6 for the x ¼ 0 alloy to 0.58 for the x ¼ 3 alloy. Measurements of the hysteresis loops for the rod samples of the Fe61 Co10 Zr5 W4 B20 alloy indicated a low value of coercivity of 2 A=m and a high value of the anisotropy field 4000 A/m which reduces the permeability of the alloy [4]. As one can expect, on increasing the Co content from 10 to 12 at%, a significant rise of the Curie temperature T C was observed; however a further increase of Co contents to 13 at% does not change T C (Fig. 3). A similar behavior of the saturation polarization with Co content was observed. Mo¨ssbauer spectroscopy measurements, carried out on 1 mm as-cast rod samples were reported by Pawlik et al. [5]. They revealed, typically for the amorphous alloys a broadening of the Mo¨ssbauer lines. The hyperfine field distribution obtained from the Mo¨ssbauer spectrum analysis consists of low- and high-field components, which suggests the coexistence of two amorphous constituent phases. In these phases, the first neighborshell surrounding the Fe atoms may contain various volume fractions of Co,
Investigation of novel Fe61 Co10þx Zr5 W4x B20 ðx ¼ 0; 2; 3Þ alloys ribbon and rod samples produced by two rapid solidification processes, revealed remarkably good glass forming abilities together with good soft magnetic properties for the alloys. An decrease of W content results in significant shift of T g and T x down to the lower temperatures, while T m remains constant; thus leading to the decrease of T g =T m . At the same time, the decrease of maximum thickness of fully amorphous samples with decrease of W contents was observed, so that fully amorphous 220 mm thick melt-spun ribbon samples and 2 mm diameter suction-cast rods were produced for the x ¼ 0 alloy. Acknowledgment This research was supported by Polish Scientific Research Committee (KBN) (project nos. 3T08A 046 27 and 3T08A028 25). References [1] A. Inoue, T. Zhang, A. Tekeuchi, Appl. Phys. Lett. 71 (1997) 464. [2] M. Stoica, J. Eckert, S. Roth, L. Schultz, Mater. Sci. Eng. A 375–377 (2004) 399. [3] H. Chiriac, N. Lupu, Mater. Sci. Eng. A 375–377 (2004) 255. [4] P. Pawlik, H.A. Davies, M.R.J. Gibbs, Appl. Phys. Lett. 83 (2003) 2775. ˙ ak, J. Zbroszczyk, J.J. Wys"ocki, [5] P. Pawlik, M. Nabia"ek, E. Z J. Olszewski, K. Pawlik, Arch. Nauki Mat. 25 (2004) 177.