Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys
  • C22C45/04—Amorphous alloys with nickel or cobalt as the major constituent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/153—Amorphous metallic alloys, e.g. glassy metals
  • H01F1/15316—Amorphous metallic alloys, e.g. glassy metals based on Co

Definitions

• This invention relates to glassy metal alloys with near-zero magnetostriction, high magnetic and thermal stability and excellent soft magnetic properties.
• Saturation magnetostriction AS is related to the fractional change in length ⁇ l/l that occurs in a magnetic material on going from the demagnetized to the saturated, ferromagnetic state.
• the value of magnetostriction a dimensionless quantity, is often given in units of microstrains (i.e., a microstrain is a fractional change in length of one part per million).
• Ferromagnetic alloys of low magnetostriction are desirable for several interrelated reasons:
• Zero magnetostrictive alloys based on the binaries but with small additions of other elements such as molybdenum, copper or aluminum to provide specific property changes. These include, for example, 4% Mo, 79% Ni, 17% Fe (sold under the designation Moly Permalloy) for increased resistivity and permeability; permalloy plus varying amounts of copper (sold under the designation Mumetal) for magnetic softness and improved ductility; and 85 wt.% Fe, 9 wt.% Si, 6 wt.% AI (sold under the designation Sendust) for zero anisotropy.
• the alloys included in category (1) are the most widely used of the three classes listed above because they combine zero magnetostriction with low anisotropy and are, therefore, extremely soft magnetically; that is they have a low coercivity, a high permeability and a low core loss. These permalloys are also relatively soft mechanically and their excellent magnetic properties, achieved by high temperature (above 1000°C) anneal, tend to be degraded by relatively mild mechanical shock.
• Category (2) alloys such as those based on Co 90 Fe 10 have a much higher saturation induction (B s about 1.9 Tesla) than the permalloys. However, they also have a strong negative magnetocrystalline anisotropy, which prevents them from being good soft magnetic materials. For example, the initial permeability of Cog o Fe lo is only about 100 to 200.
• Category (3) alloys such as Fe/6 wt% Si and the related ternary alloy Sendust (mentioned above) also show higher saturation inductions (B S about 1.8 Tesla and 1.1 Tesla, respectively) than the permalloys.
• these alloys are extremely brittle and have, therefore, found limited use in powder form only.
• compositional dependence of the magnetostriction is very strong in these materials, difficult precise tayloring of the alloy composition to achieve near-zero magnetostriction.
• glassy metal alloys of zero magnetostriction. Such alloys might be found near the compositions listed above. Because of the presence of metalloids which tend to quench the magnetization by the transfer of charge to the transition-metal d-electron states, however, glassy metal alloys based on the 80 nickel permalloys are either non-magnetic at room temperature or have unacceptably low saturation inductions.
• the glassy alloy Fe 40 Ni 40 P 14 B 6 (the subscripts are in atom percent) has a saturation induction of about 0.8 Tesla, while the glassy alloy Ni 49 Fe 29 P 14 B 6 Si 2 has a saturation induction of about 0.46 Tesla and the glassy alloy Ni 80 P 20 is non-magnetic.
• No glassy metal alloys having a saturation magnetostriction approximately equal to zero have yet been found near the iron-rich Sendust composition.
• a number of near-zero magnetostrictive glassy metal alloys based on the Co-Fe crystalline alloy mentioned above in (2) have been reported in the literature. These are, for example, Co 72 Fe 3 P 16 B 6 Al 3 (AIP Conference Proceedings, No. 24, pp.
• the saturation induction (B s ) of these alloys ranges between 0.6 and 1.2 Tesla.
• the glassy alloys with B s close to 0.6 T show low coercivities and high permeabilities comparable to crystalline supermalloys.
• these alloys tend to be magnetically unstable at relatively low (150°C) temperatures.
• the glassy alloys with B s -1.2 Tesla tend to have their ferromagnetic Curie temperatures (Of) near or above their first crystallization temperatures (T cl ). This makes heat-treatment of these materials very difficult to achieve desired soft magnetic properties because such annealing is most effective when carried out at temperatures near 6 f .
• a magnetic alloy that is at least 70% glassy, and which has a near-zero magnetostriction, high magnetic and thermal stability and excellent soft magnetic properties.
• the glassy metal alloy has the composition Co a Fe b Ni e Mo d B e Si f , where a ranges from about 58 to 70 atom percent, b ranges from about 2 to 7.5 atom percent, c ranges from about 0 to 8 atom percent, d ranges from about 1 to about 2 atom percent, e ranges from about 11 to 15 atom percent and f ranges from about 9 to 14 atom percent, with the proviso that the sum of a, b and c ranges from about 72 to 76 atom percent and the sum of e and f ranges from about 23 to 26 atom percent.
• the glassy alloy has a value of magnetostriction ranging from about -1 x10 -6 to +1 x10 -6 a saturation induction ranging from about 0.6 to 0.8 Tesla, a Curie temperature ranging from about 550 to 670K and a first crystallization temperature ranging from about 790 to 870 K.
• a magnetic alloy that is at least 70% glassy and which has an outstanding combination of properties, including a near-zero magnetostriction, high magnetic and thermal stability and such soft magnetic properties as high permeability, low core loss and low coercivity.
• the glassy metal alloy has the composition Co a Fe b Ni c Mo d B e Si f , where a ranges from about 58 to 70 atom percent, b ranges from about 2 to 7.5 atom percent, c ranges from about 0 to 8 atom percent and d ranges from about 1 to about 2 atom percent, e ranges from about 11 to 15 atom percent and f ranges from about 9 to 14 atom percent, with the proviso that the sum of a, b and c ranges from about 72 to 76 atom percent and the sum of e and f ranges from about 23 to 26 atom percent.
• the glassy alloy has a value of magnetostriction ranging from about -1x10 -6 to +1x10 -6 and a saturation induction ranging from about 0.6 to 0.8 Tesla, Curie Temperature, ranging from 550 to 670K and the first crystallization temperature ranging from about 790 to 870 K.
• molybdenum in the alloys of the invention may be replaced by at least one other transition metal element, such as tungsten, niobium, tantalum, titanium, zirconium and hafnium, and up to about 2 atom percent of Si may be replaced by carbon, aluminum or germanium without significantly degrading the desirable magnetic properties of these glassy alloys.
• Examples of essentially zero magnetostrictive glassy metal alloys of the invention include
• Some magnetic and thermal properties of these and some of other near-zero magnetostrictive glassy alloys of the present invention are listed in Table II. These may be compared with properties listed in Table I for previously-reported glassy metal alloys of zero magnetostriction.
• the activation energy (E a ) for the reorientation of the magnetization is listed in Table III for some representative near-zero magnetostrictive glassy alloys. This table indicates that Si tends to increase E a and also that E a tends to be higher when Si/B ratio is close to 1. The higher values of E a , indicating higher magnetic stability of the system, is desired. Combining these information based Table II and III, preferred Si content is between 9 and 14 atom percent when (Si+B) is between 23 and 26 atom percent.
• the presence of Mo is to increase T el and hence the thermal stability of the alloy system.
• the content of Mo beyond 2 atom percent reduces the Curie temperature to a level lower than 550 K, which is undesirable in convention magnetic devices.
• Such near-zero magnetostrictive glassy metal alloys are obtained for a, b and c in the ranges of about 58 to 70, 2 to 7.5 and 0 to 8 atom percent respectively, with the provision that the sum of a, b and c ranges between 72 and 76 atom percent.
• the absolute value of saturation magnetostriction ⁇ s of these glassy metal alloys is less than about 1x10 -6 (i.e., the saturation magnetostriction ranges from about -1 x10 -6 to +1 x10 -6 , or -1 to +1 microstrains).
• the saturation induction of these glassy alloys ranges between about 0.6 and 0.8 Tesla.
• Values of ⁇ s even closer to zero may be obtained for values of a, b and c ranging respectively from about 63 to 69, 3 to 6 and 0 to 6, with the provision that the sum of a, b and c ranges between about 72 and 76 atom percent.
• the glassy metal alloys of the invention are conveniently prepared by techniques readily available elsewhere; see, e.g., U.S. Patents 3,845,805, issued November 5,1974 and 3,856,513, issued December 24, 1974.
• the glassy alloys, in the form of continuous ribbon, wire, etc. are rapidly quenched from a melt of the desired composition at a rate of at least about 10 5 K/sec.
• a metalloid content of boron, and silicon in the range of about 23 to 26 atom percent of the total alloy composition is sufficient for glass formation, with boron ranging from about 11 to 15 atom percent and silicon ranging from about 9 to about 14 atom percent.
• a ratio Si/B close to 1 and a Si content ("f") between 11 and 12 atom percent are most favorable because they lead to higher stability and relative insensitiveness of the magnetostriction value (which is close to,zero) to the metalloid composition.
• the rate of change of magnetostriction value with respect to silicon content, dA s /df is close to zero for "f" between 11 and 12 atom percent while
• the small amount of Ni is relatively ineffective to alter the magnetostriction values in the present alloy system and Co:Fe ratios essentially determine the resultant magnetostriction values.
• Zero magnetostriction is realized for the Co:Fe ratio of about (14-16.5) to 1 in the present alloy system.
• glassy metal alloys such as Co 70.5 Fe 4.5 B 10 Si 15 and Co 74 Fe 6 B 20 .
• the ratios are narrowly set at about 14 and 12 respectively.
• Table IV gives ac core loss (L), exciting power (P e ) and permeability (p) at 0.1 Tesla induction and at 50 kHz of the near-zero magnetostrictive glassy alloys of the present invention annealed at different temperatures (T a ).
• Table V shows the effects of the annealing temperature (T a ) and annealing field (H 11 ) applied along the circumferential direction of the toroidal samples on the dc coercivity (H c ) and remanence (B r ), ac coercivity (H c ) and squareness ratio (B r /B 1 ), where B 1 is the induction at an applied field of 1 Oe at 50 kHz and ⁇ at 50 kHz and 0.1 T induction for one of the zero magnetostrictive alloys of the present invention.
• Low coercivity and high squareness ratio close to 1 at high frequencies are desirable in some magnetic device applications such as switch-mode power supplies.
• Table VI shows the effects of the annealing time (t a ) on L, Pe and ⁇ for one of the zero magnetostrictive alloys of the present invention.
• the advantageous combination of properties provided by the alloys of the present invention cannot be achieved in the prior art nonmagnetostrictive glassy alloys with high saturation induction such as Co 74 Fe 6 B 20 because their Curie temperatures are higher than the first crystallization temperatures and the heat-treatment to improve their properties are not so effective as in those with lower saturation inductions.
• the above properties, achieved in the glassy alloys of the present invention may be obtained in low induction glassy alloys of the prior art.
• these alloys of the prior art such as Co 31.2 Fe 7.8 Ni 39.0 B 14 si 8 tend to be magnetically unstable at relatively low temperature of about 150°C as pointed earlier.
• Table VII shows the magnetic properties of some of the representative glassy alloys of the composition CO a Fe b Ni c MO d B e Si f in which at least one of a, b, c, d, e, and f is outside the composition range defined in the present invention.
• the table indicates that the alloys with at least one of the constituents outside the defined ranges exhibit at least one of the following undesirable properties: (i) The value of
• the glassy alloys listed in Tables II-VII were rapidly quenched (about 10 6 K/sec) from the melt following the techniques taught by Chen and Polk in U.S. Patent 3,856,513.
• the resulting ribbons typically 25 to 30 pm thick and 0.5 to 2.5 cm wide, were determined to be free of significant crystallinity by X-ray diffractometry (using CuK radiation) and scanning calorimetry. Ribbons of the glassy metal alloys were strong, shiny, hard and ductile.
• Continuous ribbons of the glassy metal alloys prepared in accordance with the procedure described in Example I were wound onto bobbins (3.8 cm O.D.) to form closed-magnetic-path toroidal samples. Each sample contained from 1 to 3 g of ribbon. Insulated primary and secondary windings (numbering at least 10 each) were applied to the toroids. These samples were used to obtain hysteresis loops (coercivity and remanence) and initial permeability with a commercial curve tracer and core loss (IEEE Standard 106-1972).
• the ferromagnetic Curie temperature ( ⁇ f ) was measured by inductance method and also monitored by differential scanning calorimetry, which was used primarily to determine the crystallization temperatures.
• the first or primary crystallization temperature (T el ) was used to compare the thermal stability of various glassy alloys of the present and prior art inventions.
• Magnetic stability was determined from the reorientation kinetics of the magnetization, in accordance with the method described in Journal of Applied Physics, vol. 49, p. 6510 (1978), which method is incorporated herein by reference thereto.
• Magnetostriction measurements employed metallic strain gauges (BLH Electronics), which were bonded (Eastman-910 Cement) between two short lengths of ribbon. The ribbon axis and gauge axis were parallel. The magnetostriction was determined as a function of applied field from the longitudinal strain in the parallel ( ⁇ l/l) 11 and perpendicular ( ⁇ l/l) 1 in-plain fields, according to the formula

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• 1982
  • 1982-12-17 EP EP19820111754 patent/EP0084138B1/en not_active Expired
  • 1982-12-17 DE DE8282111754T patent/DE3275492D1/de not_active Expired
  • 1982-12-23 CA CA000418542A patent/CA1222647A/en not_active Expired
• 1983
  • 1983-01-18 JP JP58006529A patent/JPS58123851A/ja active Granted

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