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Positron annihilation in amorphous alloy Co58Ni10Fe5B16Si11
Scripta METALLURGICA et MATERIALIA
Vol. 29, pp. 59-62, 1993 Printed in the U.S.A.
P O S I T R O N ANNIHILATION IN A M O R P H O U S CossNi10FesB,6Sil,
Pergamon Press Ltd. All rights reserved
ALLOY
N. Nancheva*, N. Feschiev** and M. Misheva*** * Department of Physics, Technical University, Ruses 7017 ** Department of Metal Science, Technical University, Russe 7017 *** Faculty of Physics, University of Sofia, J. Bourchier blvd., Sofia 1126
(Received February 9, 1993) (Revised April 13, 1993) Introduction The amorphous alloy Co~Ni10FesB16Si11 belon~ to the group of amorphons magnetic materials with small magnetic anisotropy,which determine high magnetic permeability # and low coerciveforce He [1]. These parameters are similarto the permalloy, and exceed it for as corrosionstability,mechanical strength and electrical resistivity.Their shortcomings are connected with ageing and inabilityto accommodate the magnetic permeability.The latterincreases,the greatex the amount of vacancies. Recently the amorphous alloy,CosNi10FesB1sSi11, has become a subject of considerable interestin basic and applied research because of its unique physical and mechanical properties [3-6]. Typical applicationsare magnetic cores for various switching power supplies, senmm, magnetic heads, high-frequency transformem, magnetic shields and distribution transformers. The main disadvantages of this alloy are the low thermal stability, full unwelding and small sizes of received ribbons, wires and granules. The metallic glass ribbons are 20 to 50/~m thick, so that some grouping of layers is required - a di@icult hemdling problem. One possibility for prepearing massive pieces of work is explosive compacting of metallic glass powder, which at suitable conditions [2] does not change the mmorphous structure. A previous series of papers [3-51, summarized in [6], reported data received by magnetic crack detection. Analysis of the results showed that the explosive loading of specimens changes the structure. The theoretical description of the ionic structure is still incomplete and very little is known about the structure of defects, which strongly influence the mechanical behavour of material. Information about the structure and concentration of various imperfections can be obtained from positron emuihilation methods bec~tme it is well established that positrons are effective probes for studying vacancy type of defects ( see for example [9]). Several general reviews [10-14] summarize the main results obtained by positron annihilation in ~morphous alloys. The purlxme of the present study is to elucidate the defect structure of amorphous alloy CossNi10FesBlsSill by positron lifetime technique. Experimental The sample nmteriM was obtained from N I I C h E R M E T - Moskow in the form of ribbon with dimensions 20rnmx20,m. The chemical analysisshowed the presence of H~ (0,0075 at.%) and 02 (0.0239 ~t.°/o).Sample 1 was prepared from a ribbon. Sample 2 was prepared from an amorphous powder, from the asane ribbon, by explosive consolidation. For this purpose, an explosive loading a~embly was designed, such as that used in [7]. The size of the powder particles was ,~ 50/Jm. The amorphous structure of the ribbon and sample 2 was verified by X-ray difzaction measurements. Some characteristics of the samples investigated are shown in Table 1 [15]. For comparison, the same characteristic8 for Permalloy and Sendnst a~e presented as well.
59 0956-716X/93 $6.00 + .00 Copyright (c) 1993 Pergamon Press Ltd.
60
POSITRON
ANNIHILATION
Vol.
29, No.
TABLE 1. Magnetic Characteristics ( B . - Saturation Magnetic Induction, Hc -Coercive Force; p - Permeability), Electrical Resistivity p and Microhardnees HMV(P=50 gf) sample end treatment 1 - as received - alter TMT 2
- u received - after TMT
Permalloy( 500/oNi;50°/oFe) Permailoy(780/, Ni;22°/oFe) Sendust(84-86*/oFe; 9-10"/05i;5-60/.A1)
B0,T 0,315 0,320
Hc,A/m 10 1,9
0,450 0,298
20 5,4
1,5-1,6 0,8-1,0 1,2
4-8 1,6-6,4 3,2-4,8
#.10 -s 18 50
p, fLm 1,35.10 -e
HMV 900
6 30
3,00.10 -e 3,60.10 -e
1200
30-60 60-80 8
0,40.10 -e 0,25.10 -e 0,80.10 -4
The thermo magnetic treatment (TMT) has been made in constant (H = 800 A/m) and in the circulation magnetic field (H = 800 A/m at frequency 50 ltz). The value of H~ for the explosive consolidated sample after TMT is compatible with results in [8]. For positron lifetime measurements two identical samples with dimensloas 15xlSx2 m m ~ were used. A ~ N a radioactive source, sealed between two thin (0.723 mg/cm 2) kapton foils, was sandwiched by the samples. The positron lifetime spectrometer used is based on a fast-slow type coincidence circuit and prov/des 280 pe time resolution (FWHM). Analysis of lifetime spectra was performed by the pro~am, Positzonfit Extended [16]. About 1.2xI0 e counts were accumulated for each spectrum. The samples were measured at least 4 times. Corrections were made for source lifetime components. The measurements were carried out st room temperature in as-received samples sad for sample 2 a~ter 1 h annealing at I00, 220, 310 and 550 °C in vacuum. Before each measurement the samples were c]esaed in a suitable manner. Result, and Discussion The values of positron lifetimes and intensities, obtained by two and three, components fit ¢~ llfetlr~ spectra, are listed in Table 2. The mean lifetimes calculated from ~ = ]~ ~I~ are presented too. For c o D n , the char&cterist/c lifetimes in met~lllc constituents are also shown. TABLE 2. Positron Lifetimes sad Intensities sample end treatment 1- as received
1"~,pe Ix,°/o ~,ps 150(I) 91,3(4) 3 4 9 ( 9 )
I~,0/o
2- as received sanealingat IO0°C 220°C 310°C 550°C
162(I) 162(1) 156(I) 150(I) 144(I)
6,5(4) 2621(300) 4,8(5) S,S(6) 18~(820) 11,3(4) 1484(900) 13,1(3) 1084(360)
93,2(5) 421(6) 95,2(5)487(30) 91(1) 381(12) 88,5(4) 378(T) 88,6(4) 355(8)
8,2(4)
r~,ps 1540(260)
Is,°/o ~',ps 0,47(2) 173(2) 0,26(6) 0,~(2) 0,25(2) 0,22(2)
c~Tstal Co
bulk 118 pe [12]
wmsacy 157 p. [12]
Ni Fe
110-95 p. [9] I06 p, [9]
IS0 p. [9] IT5 p. [9]
185(2) 177(2) 179(2) 179(3)
174(2)
1
Vol.
29, No.
1
POSITRON
ANNIHILATION
61
It is well known that the basic problem in the application of positron avnihilation to the studies of metallic glasses is to achieve an understanding of the natute of positron states in these nmterials. Based on the existing knowledge [10-14; 17-20], the positron traps in metallic glasses have been identified with the vacancy-type defects, Bernal holes, quasidislocations, low-density (dilated) regions and crystalline embryos. Consequently, it can be assumed that in as-qusnched metallic glasses all positrons annihilate from the trapped states. It is evident from the experimental results (Table 2) that samples 1 and 2 have different defect structures. Our results for positron lifetimes in sample 1 are different from dat~ in [21], which nuLy be due to the different way of production and treatment of samples. The results can be summarized as follows: 1. In as-received amorphous samples I and 2, the lifetime rx is higher than values expected on the basis of the pure metal constituents of the alloy, but it is shorter than those of metal vacancies. The values of rl for samples 1 and 2 differ only 12 ps, but this is in accordance with many results in [10-14] which showed that, for amorphous alloys, the crystallization, deformation or irradiation cause much smaller effects on the annihilation characteristics than those seen in crystalline metals. 2. Component ~'2 is typical for defects llke vacancy clusters. According to [22] the number of vacancies is N = I I (for sample I) and N ~ I 9 (for sample 2). 3. The existence of a third component, I"~ ~1.5 ms, is probably connected with pick-off annihilation of o-Ps. In our opinion the formation of o-Ps is due to the presence of absorbed gases [13]. 4. The parameters obtained from a three component fit of the lifetime spectra of sample 2 after its I00 °C annealing contained considerable scatter and very large errors. Because of this, the results of the two component fit in this case are presented in Table 2. The second lifetime component can be interpreted as an apparent lifetime of mixture of two unresolved components - one probably due to pick-off annihilation of o-Ps and the second to positron annihilation in defects, like vacancy clusters. 5. With increasing of the annealing temperature, rl and I"2 decrease, while I~ increases. This could be interpreted as transferring of some of defects, orriginaUy in the I"l group into the ~2 group (cluster formation) and decreasing the size of defects like vacancy clusters. 6. The crystallization temperature of CossNi10FesB1sSi11 is 530°C [15]. From Table 2 one can see that the lifetimes and intensities in the crystalline state of the alloy are not ~astically dilfexent from those in its amorphous state after 310 °C annealing. The value of ~'I differs only 6 ps, but this is in consistent with the available results of others [10-14]. References 1. K. Sodzuki, H. Fudsimori and
K. Hasimoto in
T. Masumoto (ed),
Amorphous Metals, Metallurgi~,
Moek~ (1987) (in Ru~an) 2. R. Hnsegaws, in S. Steeb and H. Warllmont (ede), Magnetic Properties of Dynamically Compacted Glassy Metal Powder Cores. Rapidly Quenched Metals, Elsevier Science Publishers, B. V (1985) 3. R. S. Ishakov, V. I. Kirkv, A. A. Kusovnikov, A. D. Balaev, G. V. Popov emd V. P. Ovcharov, Preprint 265 F, IFSO AN, Krasnojarsk (1984) 4. P,. S. Ishakov, M. M. Ka~penko and A. A. Kusovnikov, Preprint 284 F, IFSO AN, Krasnojarsk (1984) 5. R. S. Ishskov, A. A. Kusovnikov, M.M. Karpenko and M.L.Zarjanov, Fizica tverdova tels, 28, 2, 590
(1986) 6. V.I. Kirko and A. A. Kuzovnikov, Fisica gorenija i wriv~, 6, 111 (1988) 7. M. Meyers and S. Wang, Acta Metal]., 36, 4 (1988) 8. E. Vlasov, A. Deribas, L. Korneeva, V. Nceterenko and S. Pershin, Sudostroiteln,~ja promihlenost, Metallurgia, 5, 86 (1987) 9. A. Seeger and F. Banhart, Phys. stat. sol (a), 102, 171 (1987) 10. N. Shlotani in P. G. Coleman, S. C. Sharma and L. M. Diana (eds), Positron Annihilation Proc, 6 Int. Conf., Arlington, 561 (1982) 11. P. Mcser and C. Corbel in W. Brandt (ed), Positron Solid State Physics, North - Holland Publishing Company, 679 (1983) 12. I. Ya. Dekhtyar and E . G . Madatovs in V . V . Nemmhkalenko (ed), Amorphous Metallic Alloys,
62
POSITRON
ANNIHILATION
Vol.
29, No.
Nankovs Dumk,~. Kiev, 147 (1987) (in Russ/an) 13. Ze. Kajcsoe in G. Dlubek, O. Brummer, G. Brauer and K. Hennig (eds), Proc. European Meeting on Pmitron Studies of Defects (PSD 87), Wemigerode (GDR), vol.], pezt 1, PL 5 (1987) 14. Ze. Ke~csoe, Phys. atat. sol.(,~), 102, I, 67 (1987) IS. N. Feschiev, D. Psatelseva, P. Hadgijska and I. Drsgievs, paper presented on the seminar "Dynamical E~ect on the Materials', Krasnojarsk (1990) 16. P. IGrkegaard and M. Eldrup, Comput. Phys. Comm, 7, 401 (1974) 17. T. H-nmis and E. F. Fujita, Jpn. J.Appl.Phys., 24, 249 (1985) 18. Z. Michno, T. Gorecki, Z. Kasperski and W. Swiatkowski in Ref.13, vol.2, part 1, D2 19. Z. Michno, Acts phys. poL A 72, 1,181 (1987) 20. Z. Michno, Jpn.J.Appl.Phys., 29, 5, 891 (1990) 21. R. Parejs and J.M.l~veiro in Ref. 13, vol.2, part 1, D3 22. M. J. Pusks and R. M. Nieminen, J. Phys. F; Mete] Phys., 13, 333 (1983)
i
Vol. 29, pp. 59-62, 1993 Printed in the U.S.A.
P O S I T R O N ANNIHILATION IN A M O R P H O U S CossNi10FesB,6Sil,
Pergamon Press Ltd. All rights reserved
ALLOY
N. Nancheva*, N. Feschiev** and M. Misheva*** * Department of Physics, Technical University, Ruses 7017 ** Department of Metal Science, Technical University, Russe 7017 *** Faculty of Physics, University of Sofia, J. Bourchier blvd., Sofia 1126
(Received February 9, 1993) (Revised April 13, 1993) Introduction The amorphous alloy Co~Ni10FesB16Si11 belon~ to the group of amorphons magnetic materials with small magnetic anisotropy,which determine high magnetic permeability # and low coerciveforce He [1]. These parameters are similarto the permalloy, and exceed it for as corrosionstability,mechanical strength and electrical resistivity.Their shortcomings are connected with ageing and inabilityto accommodate the magnetic permeability.The latterincreases,the greatex the amount of vacancies. Recently the amorphous alloy,CosNi10FesB1sSi11, has become a subject of considerable interestin basic and applied research because of its unique physical and mechanical properties [3-6]. Typical applicationsare magnetic cores for various switching power supplies, senmm, magnetic heads, high-frequency transformem, magnetic shields and distribution transformers. The main disadvantages of this alloy are the low thermal stability, full unwelding and small sizes of received ribbons, wires and granules. The metallic glass ribbons are 20 to 50/~m thick, so that some grouping of layers is required - a di@icult hemdling problem. One possibility for prepearing massive pieces of work is explosive compacting of metallic glass powder, which at suitable conditions [2] does not change the mmorphous structure. A previous series of papers [3-51, summarized in [6], reported data received by magnetic crack detection. Analysis of the results showed that the explosive loading of specimens changes the structure. The theoretical description of the ionic structure is still incomplete and very little is known about the structure of defects, which strongly influence the mechanical behavour of material. Information about the structure and concentration of various imperfections can be obtained from positron emuihilation methods bec~tme it is well established that positrons are effective probes for studying vacancy type of defects ( see for example [9]). Several general reviews [10-14] summarize the main results obtained by positron annihilation in ~morphous alloys. The purlxme of the present study is to elucidate the defect structure of amorphous alloy CossNi10FesBlsSill by positron lifetime technique. Experimental The sample nmteriM was obtained from N I I C h E R M E T - Moskow in the form of ribbon with dimensions 20rnmx20,m. The chemical analysisshowed the presence of H~ (0,0075 at.%) and 02 (0.0239 ~t.°/o).Sample 1 was prepared from a ribbon. Sample 2 was prepared from an amorphous powder, from the asane ribbon, by explosive consolidation. For this purpose, an explosive loading a~embly was designed, such as that used in [7]. The size of the powder particles was ,~ 50/Jm. The amorphous structure of the ribbon and sample 2 was verified by X-ray difzaction measurements. Some characteristics of the samples investigated are shown in Table 1 [15]. For comparison, the same characteristic8 for Permalloy and Sendnst a~e presented as well.
59 0956-716X/93 $6.00 + .00 Copyright (c) 1993 Pergamon Press Ltd.
60
POSITRON
ANNIHILATION
Vol.
29, No.
TABLE 1. Magnetic Characteristics ( B . - Saturation Magnetic Induction, Hc -Coercive Force; p - Permeability), Electrical Resistivity p and Microhardnees HMV(P=50 gf) sample end treatment 1 - as received - alter TMT 2
- u received - after TMT
Permalloy( 500/oNi;50°/oFe) Permailoy(780/, Ni;22°/oFe) Sendust(84-86*/oFe; 9-10"/05i;5-60/.A1)
B0,T 0,315 0,320
Hc,A/m 10 1,9
0,450 0,298
20 5,4
1,5-1,6 0,8-1,0 1,2
4-8 1,6-6,4 3,2-4,8
#.10 -s 18 50
p, fLm 1,35.10 -e
HMV 900
6 30
3,00.10 -e 3,60.10 -e
1200
30-60 60-80 8
0,40.10 -e 0,25.10 -e 0,80.10 -4
The thermo magnetic treatment (TMT) has been made in constant (H = 800 A/m) and in the circulation magnetic field (H = 800 A/m at frequency 50 ltz). The value of H~ for the explosive consolidated sample after TMT is compatible with results in [8]. For positron lifetime measurements two identical samples with dimensloas 15xlSx2 m m ~ were used. A ~ N a radioactive source, sealed between two thin (0.723 mg/cm 2) kapton foils, was sandwiched by the samples. The positron lifetime spectrometer used is based on a fast-slow type coincidence circuit and prov/des 280 pe time resolution (FWHM). Analysis of lifetime spectra was performed by the pro~am, Positzonfit Extended [16]. About 1.2xI0 e counts were accumulated for each spectrum. The samples were measured at least 4 times. Corrections were made for source lifetime components. The measurements were carried out st room temperature in as-received samples sad for sample 2 a~ter 1 h annealing at I00, 220, 310 and 550 °C in vacuum. Before each measurement the samples were c]esaed in a suitable manner. Result, and Discussion The values of positron lifetimes and intensities, obtained by two and three, components fit ¢~ llfetlr~ spectra, are listed in Table 2. The mean lifetimes calculated from ~ = ]~ ~I~ are presented too. For c o D n , the char&cterist/c lifetimes in met~lllc constituents are also shown. TABLE 2. Positron Lifetimes sad Intensities sample end treatment 1- as received
1"~,pe Ix,°/o ~,ps 150(I) 91,3(4) 3 4 9 ( 9 )
I~,0/o
2- as received sanealingat IO0°C 220°C 310°C 550°C
162(I) 162(1) 156(I) 150(I) 144(I)
6,5(4) 2621(300) 4,8(5) S,S(6) 18~(820) 11,3(4) 1484(900) 13,1(3) 1084(360)
93,2(5) 421(6) 95,2(5)487(30) 91(1) 381(12) 88,5(4) 378(T) 88,6(4) 355(8)
8,2(4)
r~,ps 1540(260)
Is,°/o ~',ps 0,47(2) 173(2) 0,26(6) 0,~(2) 0,25(2) 0,22(2)
c~Tstal Co
bulk 118 pe [12]
wmsacy 157 p. [12]
Ni Fe
110-95 p. [9] I06 p, [9]
IS0 p. [9] IT5 p. [9]
185(2) 177(2) 179(2) 179(3)
174(2)
1
Vol.
29, No.
1
POSITRON
ANNIHILATION
61
It is well known that the basic problem in the application of positron avnihilation to the studies of metallic glasses is to achieve an understanding of the natute of positron states in these nmterials. Based on the existing knowledge [10-14; 17-20], the positron traps in metallic glasses have been identified with the vacancy-type defects, Bernal holes, quasidislocations, low-density (dilated) regions and crystalline embryos. Consequently, it can be assumed that in as-qusnched metallic glasses all positrons annihilate from the trapped states. It is evident from the experimental results (Table 2) that samples 1 and 2 have different defect structures. Our results for positron lifetimes in sample 1 are different from dat~ in [21], which nuLy be due to the different way of production and treatment of samples. The results can be summarized as follows: 1. In as-received amorphous samples I and 2, the lifetime rx is higher than values expected on the basis of the pure metal constituents of the alloy, but it is shorter than those of metal vacancies. The values of rl for samples 1 and 2 differ only 12 ps, but this is in accordance with many results in [10-14] which showed that, for amorphous alloys, the crystallization, deformation or irradiation cause much smaller effects on the annihilation characteristics than those seen in crystalline metals. 2. Component ~'2 is typical for defects llke vacancy clusters. According to [22] the number of vacancies is N = I I (for sample I) and N ~ I 9 (for sample 2). 3. The existence of a third component, I"~ ~1.5 ms, is probably connected with pick-off annihilation of o-Ps. In our opinion the formation of o-Ps is due to the presence of absorbed gases [13]. 4. The parameters obtained from a three component fit of the lifetime spectra of sample 2 after its I00 °C annealing contained considerable scatter and very large errors. Because of this, the results of the two component fit in this case are presented in Table 2. The second lifetime component can be interpreted as an apparent lifetime of mixture of two unresolved components - one probably due to pick-off annihilation of o-Ps and the second to positron annihilation in defects, like vacancy clusters. 5. With increasing of the annealing temperature, rl and I"2 decrease, while I~ increases. This could be interpreted as transferring of some of defects, orriginaUy in the I"l group into the ~2 group (cluster formation) and decreasing the size of defects like vacancy clusters. 6. The crystallization temperature of CossNi10FesB1sSi11 is 530°C [15]. From Table 2 one can see that the lifetimes and intensities in the crystalline state of the alloy are not ~astically dilfexent from those in its amorphous state after 310 °C annealing. The value of ~'I differs only 6 ps, but this is in consistent with the available results of others [10-14]. References 1. K. Sodzuki, H. Fudsimori and
K. Hasimoto in
T. Masumoto (ed),
Amorphous Metals, Metallurgi~,
Moek~ (1987) (in Ru~an) 2. R. Hnsegaws, in S. Steeb and H. Warllmont (ede), Magnetic Properties of Dynamically Compacted Glassy Metal Powder Cores. Rapidly Quenched Metals, Elsevier Science Publishers, B. V (1985) 3. R. S. Ishakov, V. I. Kirkv, A. A. Kusovnikov, A. D. Balaev, G. V. Popov emd V. P. Ovcharov, Preprint 265 F, IFSO AN, Krasnojarsk (1984) 4. P,. S. Ishakov, M. M. Ka~penko and A. A. Kusovnikov, Preprint 284 F, IFSO AN, Krasnojarsk (1984) 5. R. S. Ishskov, A. A. Kusovnikov, M.M. Karpenko and M.L.Zarjanov, Fizica tverdova tels, 28, 2, 590
(1986) 6. V.I. Kirko and A. A. Kuzovnikov, Fisica gorenija i wriv~, 6, 111 (1988) 7. M. Meyers and S. Wang, Acta Metal]., 36, 4 (1988) 8. E. Vlasov, A. Deribas, L. Korneeva, V. Nceterenko and S. Pershin, Sudostroiteln,~ja promihlenost, Metallurgia, 5, 86 (1987) 9. A. Seeger and F. Banhart, Phys. stat. sol (a), 102, 171 (1987) 10. N. Shlotani in P. G. Coleman, S. C. Sharma and L. M. Diana (eds), Positron Annihilation Proc, 6 Int. Conf., Arlington, 561 (1982) 11. P. Mcser and C. Corbel in W. Brandt (ed), Positron Solid State Physics, North - Holland Publishing Company, 679 (1983) 12. I. Ya. Dekhtyar and E . G . Madatovs in V . V . Nemmhkalenko (ed), Amorphous Metallic Alloys,
62
POSITRON
ANNIHILATION
Vol.
29, No.
Nankovs Dumk,~. Kiev, 147 (1987) (in Russ/an) 13. Ze. Kajcsoe in G. Dlubek, O. Brummer, G. Brauer and K. Hennig (eds), Proc. European Meeting on Pmitron Studies of Defects (PSD 87), Wemigerode (GDR), vol.], pezt 1, PL 5 (1987) 14. Ze. Ke~csoe, Phys. atat. sol.(,~), 102, I, 67 (1987) IS. N. Feschiev, D. Psatelseva, P. Hadgijska and I. Drsgievs, paper presented on the seminar "Dynamical E~ect on the Materials', Krasnojarsk (1990) 16. P. IGrkegaard and M. Eldrup, Comput. Phys. Comm, 7, 401 (1974) 17. T. H-nmis and E. F. Fujita, Jpn. J.Appl.Phys., 24, 249 (1985) 18. Z. Michno, T. Gorecki, Z. Kasperski and W. Swiatkowski in Ref.13, vol.2, part 1, D2 19. Z. Michno, Acts phys. poL A 72, 1,181 (1987) 20. Z. Michno, Jpn.J.Appl.Phys., 29, 5, 891 (1990) 21. R. Parejs and J.M.l~veiro in Ref. 13, vol.2, part 1, D3 22. M. J. Pusks and R. M. Nieminen, J. Phys. F; Mete] Phys., 13, 333 (1983)
i