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Investigation of influence of micro-structure on magnetic properties of amorphous powder core
RARE METALS Vol. 25, Spec. Issue. Oct 2006, p .458
Investigation of influence of micro-structure on magnetic properties of amorphous powder core GUO Feng" , BA Shan') , LJ Deren') , LU Zhichao]', LU Caowei'), and WANG Jun') I ) Central Iron and Steel Research Institute, Advanced Technology & Materials C o . , Ltd., Beijing 100081, China 2 ) Beijing Institute of Technology, School of Science, Beijing 100081, China (Received 2006-06-25) Abstract: The influence of micro-structure on magnetic properties of amorphous powder core was investigated. The results show that the amorphous powders of the powder core become crystallized with the increase of annealing temperature, and the permeability decreases from 60 to 12, the core loss increases from 0 . 2 to 0 . 3 W * cm 3 , DC-bias characteristic was improved with further increase of annealing temperature, and the magnetic properties become deteriorated due to decrease of permeability and enhancement of coercive force resulting from the crystallization of amorphous powder.
Key words : amorphous powder core ; core loss; permeability ; DC-bias characteristic ; annealing
[ This work was financially supported by Beijing Municipal Science and Techmlogy Program ( N o . DO405003040121 1 . 3
1 . Introduction The powder core is made of magnetic powder and insulation materials and then pressed into shape of annulus or E , etc. Conventional powder cores include MPP High Flux and FeSiAl , and the important parameters to evaluated powder core are core loss, permeability and DC-bias characteristic [ 1-41. Improvement of magnetic properties and reducing of cost are always required. Fe-based amorphous alloys exhibit excellent soft magnetic properties[ 51 , and have lower cost. In this paper, the influence of micro-structure on magnetic properties of Febased amorphous powder core was investigated.
2.
The magnetic properties were measured later. The permeability and character factor Q were measured by Agenllent4294A, and the root mean square current is 3 mA. The DC-bias characteristic was measured by Agenllent4284A, and the DC-bias force is from 0 250 Oe, the testing frequency is 100
-
kHz . The core loss of powder cores was measured by walker AC magnetic tester. The testing frequency was 100 kHz and the flux density was 0.1 T. Crystal structure was measured by DSdiscover, and the 28 was from 20"-90". T , was measured by N E T C Z H W . The testing temperature was from 20 to 600 T , and the temperature ascending rate was 20 Kmmin-'.
Experimental
The amorphous powder with nominal composition of Fe,, AI,Sn2PlOC2B& was prepared bj- water atomizing. The amorphous powder core were made from the mixture of amorphous powder with 2 % epoxy resin. Corresponding author : GUO Feng
3.
Results and discussion
3.1. Measuring results of amorphous powder Observing the Fig. 1, the structure of powder is amorphous, and the T , and T , are 476.0
E-mail: guofeng@atmcn .corn
.
Guo F et al . , Influence of micro-structure on magnetic properties of powder core
459
“c [ 111 and 353.3 “c [ 11] respectively
3 . 2 . Influence of micro-structure on permeability Above T , the amorphous powder core will occur crystallization(Figs. 3( a ) and ( b ) ) , and its magnetic properties are changed. Fig. 2 shows the permeability of amorphous powder core annealed at different temperatures, and permeability decreases from 60 to 12 above T , at whole range of testing frequency. This is because crystallization results in FezB or Fe3B and a-Fe[ 111 depositing from amorphous powder. Moreover, FezB and Fe3B are non-magnetic and these depositions damp down material’s magnetic properties[ 8-91 , therefore its coercive force rises and accordingly permeability decreases.
3.3. Influence of micro-structure on core loss m-0-
100 K
@.4 200 K ’
4500 K
-.-0
50-
a”
30-
a
e
‘
-v-1000K -0-5000 K
P.
-
0
10
+ , . , . , . , . , . , .
2 U/(”)
Fig. 1.
XRD spectrum for amorphous powder.
1.5
Temperature1‘C
Fig.2.
Effect of micro-structure on permeability.
(1) 400 “C
(2) 480 “C 4
TemperatureE
2 ”(”)
Fig.3. Structure change of amorphous powder core at different annealing temperatures: ( a ) DSC curve at different temperatures; (b) crystal structure at different temperatures.
RARE METALS, Vol. 25, Spec. Issue, Oct 2006
460
loss is dominating. For powder core annealing above T,, core loss is descending at 1000 kHz comparing with the one’s at 100 and 200 kHz (Table 1 ) . This is because of the L becoming lower sharply comparing with lower frequency.
is. At the lower frequency, core loss is composed of hysteresis loss dominantly, R is invariable and the higher the R the higher core loss. All these result in increasing of core loss with frequency( Fig. 4( b) ) . While at higher frequency, eddy-current Table 1. Effect of micro-structure on Q Annealing temperature
f = 100 kHz
f = 200 kHz
f = 500 kHz
20 g: 360 T
16.49 34.01 43.73 35.91 12.86 11.22
27.51 54.57 50.60 43.56 21.24 19.02
45.56 86.24 38.66 34.62 35.30 31.93
400°C 440 “C 480 C
520 T
f = lo00 kHz f = 5000 kHz 50.02 56.63 5.656 5.11 39.29 34.44
56.56 100.87 23.71 21.69 44.05 39.90
J
W-
8 2
w.
M
w,
Temperature/“C
aml
.
o
. , ~
p
.
,
I
.
H
.)
. o .r
o
o
u
Temperaturd ‘C
Frequency /KHz
Fig. 4. Effect of micro-structure on core loss : (a) effect of annealing at different frequency ; (b) effect of frequency on core loss; ( c ) innwnce of temperature on coercive force (100 kHz)
.
3.4. Influence of micro structure on DC-bias characteristic Below the temperature T , , DC-bias characteristic gradually descends and then improves a little above the temperature T,( Fig. 5 ) . The reason is that coercive force descends below T , and above T , coercive force becomes rising( Fig. 4 ( d ) ) . When there is a DC-bias magnetizing force, the smaller coercive force the more sensitive inductance, so while above T, DC-bias character is improved. The other reason is that when there is a DC-bias magnetizing force, the inductance of amorphous powder core can be disturbed seriously and the higher DC-bias magnetizing force, the more seriously. All these show that coercive force and inductance together influence DC-bias character of amorphous powder core.
i 0
.d
-2
-
apr \ 204-6# 0
50
loo
150
200
250
Tcmperaturc/’C
Fig.5. acter.
4.
Effect of microstructure on DC-bias char-
Conclusions
(1) The effect of micro structure on permeability for amorphous powder core is divided into two situation. At the first place, while an-
Guo F . et al . , Muence of micro-structure on magnetic properties of powder core
nealing below T,, when the annealing temperature is increased, coercive force becomes descending which is because of relaxation of residual stress and paramagnetism-transition above T , . Then above T,, crystallization and structure relaxation result in increasing of coercive force and so permeability begins decreasing. (2) The effect of micro structure on permeability for amorphous powder core is divided into two situation. Below T,, the reasons for coercive force decreasing are relaxation of residual stress and paramagnetism-transition above T , . And above T , , crystallization and structure relaxation result in increasing of coercive force and resistance, so hysteresis loss and eddy current loss increase. (3) The effect of micro structure on DCbias character for amorphous powder core is due to the change of coercive and inductance.
References [ 11 Yagi M . , and Endo I. , Magnetic properties of Fe-based amorphous powder cores produced by a hot-pressing method. Journal of Magnetism and Magnetic Materials, 2000, 215 216: 284. [2] Dobrzanskia L. A . , and Nowosielskia R. , Properties and structure of the toroidal magnetically soft cores made fmm the amorphous strips, powder, and composite materials. Jownal of Materials Processing Technology, 2004, 157 - 158: 669.
-
461
[ 31 Lefebvre L. P . , Effect of electrical resistivety on core losses in soft magnetic iron powder materials. Jounu~lof Magnetism and Magnetic Muteri~ l ,s1997, 196: L93. [41 Raja M . Manivel, Soft magnetic properties of nanostructured FINEMET alloy powder cores. Materials Science and Engineering, 2001, A304 -306: 1062. [51 Zhang Liang, Preparation and properties of bulk L~B~C~ amorphous F ~ ~ * - ~ , C ~ , M O , S ~ ~ P (~xO=S2, 4) alloys. Journal of Magnetism and Magnetic Materials, 2004, 11: 1. [6] Dobna’nski L. A . , Properties and structure of the toroidal magnetically soft cores made from the amorphous strips, powder, and composite materials. Journal of Materials Processing Technology, 2004, 157-158: 669. [7] Shoji Yoshida, Structure and soft magnetic properties of bulk Fe-Al-Ga-P-C-B-Si glassy alloys prepared by consolidating amorphous powders. Materials Science and Engineering, 2001, A304 -306: 1019. 181 Kollar P. , Structure and magnetic properties of hot pressed Co-based powder. Journal of Magnetism and Magnetic Materials , 2004, 278: 373. [9] Pu Jian, Kinetics crystallization of bulk Pd77.5 cU6sil6.5 amorphous alloys. Chinese Journal of RareMetals (inchinese), 2003, 27(06): 571. [ 101 Guo Yicheng, and Wang Zhenxi, Amorphous Physics, Science Publishing Company, Beijing , 1984: 370. [ l l ] Lu Caowei, Investigation of amorphous powder for nominal composition Fe74 A&Sn2Plo C2B4Si4 and its powder core. Chinese Physics, 2006, 55 ( 5 ) : 2553.
Investigation of influence of micro-structure on magnetic properties of amorphous powder core GUO Feng" , BA Shan') , LJ Deren') , LU Zhichao]', LU Caowei'), and WANG Jun') I ) Central Iron and Steel Research Institute, Advanced Technology & Materials C o . , Ltd., Beijing 100081, China 2 ) Beijing Institute of Technology, School of Science, Beijing 100081, China (Received 2006-06-25) Abstract: The influence of micro-structure on magnetic properties of amorphous powder core was investigated. The results show that the amorphous powders of the powder core become crystallized with the increase of annealing temperature, and the permeability decreases from 60 to 12, the core loss increases from 0 . 2 to 0 . 3 W * cm 3 , DC-bias characteristic was improved with further increase of annealing temperature, and the magnetic properties become deteriorated due to decrease of permeability and enhancement of coercive force resulting from the crystallization of amorphous powder.
Key words : amorphous powder core ; core loss; permeability ; DC-bias characteristic ; annealing
[ This work was financially supported by Beijing Municipal Science and Techmlogy Program ( N o . DO405003040121 1 . 3
1 . Introduction The powder core is made of magnetic powder and insulation materials and then pressed into shape of annulus or E , etc. Conventional powder cores include MPP High Flux and FeSiAl , and the important parameters to evaluated powder core are core loss, permeability and DC-bias characteristic [ 1-41. Improvement of magnetic properties and reducing of cost are always required. Fe-based amorphous alloys exhibit excellent soft magnetic properties[ 51 , and have lower cost. In this paper, the influence of micro-structure on magnetic properties of Febased amorphous powder core was investigated.
2.
The magnetic properties were measured later. The permeability and character factor Q were measured by Agenllent4294A, and the root mean square current is 3 mA. The DC-bias characteristic was measured by Agenllent4284A, and the DC-bias force is from 0 250 Oe, the testing frequency is 100
-
kHz . The core loss of powder cores was measured by walker AC magnetic tester. The testing frequency was 100 kHz and the flux density was 0.1 T. Crystal structure was measured by DSdiscover, and the 28 was from 20"-90". T , was measured by N E T C Z H W . The testing temperature was from 20 to 600 T , and the temperature ascending rate was 20 Kmmin-'.
Experimental
The amorphous powder with nominal composition of Fe,, AI,Sn2PlOC2B& was prepared bj- water atomizing. The amorphous powder core were made from the mixture of amorphous powder with 2 % epoxy resin. Corresponding author : GUO Feng
3.
Results and discussion
3.1. Measuring results of amorphous powder Observing the Fig. 1, the structure of powder is amorphous, and the T , and T , are 476.0
E-mail: guofeng@atmcn .corn
.
Guo F et al . , Influence of micro-structure on magnetic properties of powder core
459
“c [ 111 and 353.3 “c [ 11] respectively
3 . 2 . Influence of micro-structure on permeability Above T , the amorphous powder core will occur crystallization(Figs. 3( a ) and ( b ) ) , and its magnetic properties are changed. Fig. 2 shows the permeability of amorphous powder core annealed at different temperatures, and permeability decreases from 60 to 12 above T , at whole range of testing frequency. This is because crystallization results in FezB or Fe3B and a-Fe[ 111 depositing from amorphous powder. Moreover, FezB and Fe3B are non-magnetic and these depositions damp down material’s magnetic properties[ 8-91 , therefore its coercive force rises and accordingly permeability decreases.
3.3. Influence of micro-structure on core loss m-0-
100 K
@.4 200 K ’
4500 K
-.-0
50-
a”
30-
a
e
‘
-v-1000K -0-5000 K
P.
-
0
10
+ , . , . , . , . , . , .
2 U/(”)
Fig. 1.
XRD spectrum for amorphous powder.
1.5
Temperature1‘C
Fig.2.
Effect of micro-structure on permeability.
(1) 400 “C
(2) 480 “C 4
TemperatureE
2 ”(”)
Fig.3. Structure change of amorphous powder core at different annealing temperatures: ( a ) DSC curve at different temperatures; (b) crystal structure at different temperatures.
RARE METALS, Vol. 25, Spec. Issue, Oct 2006
460
loss is dominating. For powder core annealing above T,, core loss is descending at 1000 kHz comparing with the one’s at 100 and 200 kHz (Table 1 ) . This is because of the L becoming lower sharply comparing with lower frequency.
is. At the lower frequency, core loss is composed of hysteresis loss dominantly, R is invariable and the higher the R the higher core loss. All these result in increasing of core loss with frequency( Fig. 4( b) ) . While at higher frequency, eddy-current Table 1. Effect of micro-structure on Q Annealing temperature
f = 100 kHz
f = 200 kHz
f = 500 kHz
20 g: 360 T
16.49 34.01 43.73 35.91 12.86 11.22
27.51 54.57 50.60 43.56 21.24 19.02
45.56 86.24 38.66 34.62 35.30 31.93
400°C 440 “C 480 C
520 T
f = lo00 kHz f = 5000 kHz 50.02 56.63 5.656 5.11 39.29 34.44
56.56 100.87 23.71 21.69 44.05 39.90
J
W-
8 2
w.
M
w,
Temperature/“C
aml
.
o
. , ~
p
.
,
I
.
H
.)
. o .r
o
o
u
Temperaturd ‘C
Frequency /KHz
Fig. 4. Effect of micro-structure on core loss : (a) effect of annealing at different frequency ; (b) effect of frequency on core loss; ( c ) innwnce of temperature on coercive force (100 kHz)
.
3.4. Influence of micro structure on DC-bias characteristic Below the temperature T , , DC-bias characteristic gradually descends and then improves a little above the temperature T,( Fig. 5 ) . The reason is that coercive force descends below T , and above T , coercive force becomes rising( Fig. 4 ( d ) ) . When there is a DC-bias magnetizing force, the smaller coercive force the more sensitive inductance, so while above T, DC-bias character is improved. The other reason is that when there is a DC-bias magnetizing force, the inductance of amorphous powder core can be disturbed seriously and the higher DC-bias magnetizing force, the more seriously. All these show that coercive force and inductance together influence DC-bias character of amorphous powder core.
i 0
.d
-2
-
apr \ 204-6# 0
50
loo
150
200
250
Tcmperaturc/’C
Fig.5. acter.
4.
Effect of microstructure on DC-bias char-
Conclusions
(1) The effect of micro structure on permeability for amorphous powder core is divided into two situation. At the first place, while an-
Guo F . et al . , Muence of micro-structure on magnetic properties of powder core
nealing below T,, when the annealing temperature is increased, coercive force becomes descending which is because of relaxation of residual stress and paramagnetism-transition above T , . Then above T,, crystallization and structure relaxation result in increasing of coercive force and so permeability begins decreasing. (2) The effect of micro structure on permeability for amorphous powder core is divided into two situation. Below T,, the reasons for coercive force decreasing are relaxation of residual stress and paramagnetism-transition above T , . And above T , , crystallization and structure relaxation result in increasing of coercive force and resistance, so hysteresis loss and eddy current loss increase. (3) The effect of micro structure on DCbias character for amorphous powder core is due to the change of coercive and inductance.
References [ 11 Yagi M . , and Endo I. , Magnetic properties of Fe-based amorphous powder cores produced by a hot-pressing method. Journal of Magnetism and Magnetic Materials, 2000, 215 216: 284. [2] Dobrzanskia L. A . , and Nowosielskia R. , Properties and structure of the toroidal magnetically soft cores made fmm the amorphous strips, powder, and composite materials. Jownal of Materials Processing Technology, 2004, 157 - 158: 669.
-
461
[ 31 Lefebvre L. P . , Effect of electrical resistivety on core losses in soft magnetic iron powder materials. Jounu~lof Magnetism and Magnetic Muteri~ l ,s1997, 196: L93. [41 Raja M . Manivel, Soft magnetic properties of nanostructured FINEMET alloy powder cores. Materials Science and Engineering, 2001, A304 -306: 1062. [51 Zhang Liang, Preparation and properties of bulk L~B~C~ amorphous F ~ ~ * - ~ , C ~ , M O , S ~ ~ P (~xO=S2, 4) alloys. Journal of Magnetism and Magnetic Materials, 2004, 11: 1. [6] Dobna’nski L. A . , Properties and structure of the toroidal magnetically soft cores made from the amorphous strips, powder, and composite materials. Journal of Materials Processing Technology, 2004, 157-158: 669. [7] Shoji Yoshida, Structure and soft magnetic properties of bulk Fe-Al-Ga-P-C-B-Si glassy alloys prepared by consolidating amorphous powders. Materials Science and Engineering, 2001, A304 -306: 1019. 181 Kollar P. , Structure and magnetic properties of hot pressed Co-based powder. Journal of Magnetism and Magnetic Materials , 2004, 278: 373. [9] Pu Jian, Kinetics crystallization of bulk Pd77.5 cU6sil6.5 amorphous alloys. Chinese Journal of RareMetals (inchinese), 2003, 27(06): 571. [ 101 Guo Yicheng, and Wang Zhenxi, Amorphous Physics, Science Publishing Company, Beijing , 1984: 370. [ l l ] Lu Caowei, Investigation of amorphous powder for nominal composition Fe74 A&Sn2Plo C2B4Si4 and its powder core. Chinese Physics, 2006, 55 ( 5 ) : 2553.