US3860458A

US3860458A - Method of making a magnetic body

Info

Publication number: US3860458A
Application number: US274724A
Authority: US
Inventors: Kiyoshi Inoue; Hideo Kaneko
Original assignee: Ishifuku Metal Industry Co Ltd
Current assignee: Ishifuku Metal Industry Co Ltd
Priority date: 1965-02-26
Filing date: 1972-07-24
Publication date: 1975-01-14
Anticipated expiration: 1992-01-14

Abstract

A magnetic material of high retentive capacity consisting essentially of 40 to 60 atomic percent platinum with good results when the Pt proportion is 45 to 55 atomic percent, balance cobalt (preferably 50 atomic percent + OR - 1 atomic percent platinum and 50 atomic percent + OR - 1 atomic percent cobalt), constituting a platinum/cobalt component and present as the balance of the magnetic material with between 4 and 15 atomic percent iron alone or with up to 5 atomic percent nickel (preferably above 0.1 atomic percent), the latter being present with or without copper in an amount up to 5 atomic percent copper (preferably at least 0.01 atomic percent) in the magnetic alloy. The cobalt proportion is in excess of the iron (in terms of atomic percent).

Description

United States Patent [1 1 Inoue et al.

1 1 ,Jan. 14, 19.75

[ METHOD OF MAKING A MAGNETIC BODY [75] Inventors: Kiyoshi lnoue; Hideo Kaneko, both of Tokyo, Japan [73] Assignee: lshijuku Kinzoki Kogyo K.K.,

Tokyo, Japan [22] Filed: July 24, 1972 [21] Appl. No.: 274,724

Related US. Application Data [60] Division of Ser. No. 138,081, April 4, 1971, Pat. No. 3,689,254, which is a continuation-in-part of Ser. No. 859,354, Sept, 19, 1969, abandoned, which is a continuation-in-part of Ser. No. 628,086, April 3, 1967, abandoned.

[30] Foreign Application Priority Data [58] Field of Search 148/3155, 120, 121, 31.57; 75/170, 172 R, 172 E [56] References Cited UNITED STATES PATENTS 2,514,765 7/1950 Hill 75/172 R Primary ExaminerWalter R. Satterfield Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno [57] ABSTRACT A magnetic material of high retentive capacity consisting essentially of 40 to 60 atomic percent platinum with good results when the Pt proportion is 45 to 55 atomic percent, balance cobalt (preferably 50 atomic percent 1 1 atomic percent platinum and 50 atomic percent i 1 atomic percent cobalt), constituting a platinum/cobalt component and present as the balance of the magnetic material with between 4 and 15 atomic percent iron'alone or with up to 5 atomic percent nickel (preferably above 0.1 atomic percent), the latter being present with or without copper in an amount up to 5 atomic percent copper (preferably at least 0.01 atomic percent) in the magnetic alloy. The cobalt proportion is in excess of the iron (in terms of atomic percent).

1 Claim, 7 Drawing Figures PATENTEDJAM 4% 3'. 860,458

SHEET 2 OF 2 METHOD or MAKING A MAGNETICYBODY CROSS-REFERENCE TO COPENDING APPLICATION This application is a division of applicaton Ser. No. 138,081 (now US. Pat. No. 3,689,254) filed April 4, 1971 as a continuation-in-part of application Ser. No. 859,354 of Sept. 19, 1969 (now abandoned) which in turn is a continuation-in-part of application Ser. No. 628,086 filed April 3, 1967 (now abandoned).

FIELD OF THE INVENTION Our present invention relates to improvements in platinum-cobalt-iron magnetic materials and, more particularly, to permanent-magnetic substances consisting at least in major part of nonferrous materials.

BACKGROUND OF THE INVENTION Recent investigations into binary, ternary and other multicomponent metallic alloys have revealed that many of these alloys have magnetic properties in terms of magnetic retentivity and permeability (magnetic field strength H and magnetic flux density B) far exceeding those of ferromagnetic materials in spite of the fact that such materials have long been considered the mainstay of permanent-magnet substances and compositions.

For example, it has been observed that iron/cobalt alloys, in which part of the iron of the metallurgical crystal structure is replaced by cobalt, have greater retentive powrs than the pure iron. This is indeed surprising in view of the fact that cobalt has substantially less magnetic character than iron in its elemental state. Investigations have also shown that manganese/bismuth and manganese/aluminum alloys likewise have magnetic properties resembling to a large measure alloys containing iron. It has been determined that platinumcontaining bodies with metals of the iron group likewise have good magnetic properties although when platinum is substituted for cobalt in combination with iron, the magnetic properties are only slightly better than those of the iron/cobalt alloys.

OBJECTS OF THE INVENTION It is the principal object of the present invention to provide magnetic materials and bodies composed therefrom having high magnetic remanence and magnetic retentivity as well as exceptionally strong magnetic field strength.

Another object of this invention is to provide a magnetic material and method of working same which will impart a high magnetic energy product (BXH) thereto.

SUMMARY OF THE INVENTION We have now found that an improved magnetic material consists predominantly of a platinum/cobalt/iron component containing 40 to 60 atomic percent platinum and in combination therewith a relatively high atomic proportion of iron, i.e. at least 4 atomic percent and up to 15 atomic percent with up to 5 atomic percent each of copper and/or nickel, the balance being cobalt in an amount in atomic percent greater than that of the iron (i.e. at least 4 atomic percent and up to 56 atomic percent).

Surprisingly, while iron/platinum alloys have only slightly better magnetic characteristics than iron/cobalt alloys and iron is vastly superior to cobalt in the unalloyed state with respect to the magnetic-field strength H of permanent magnets made from the respective materials, a platinum/cobalt/iron alloy has a magnetic field strength generally several times greater than that of corresponding platinum/iron alloys and the corre sponding iron/cobalt alloy, the magnetic field characteristics being improved still more when the platinum/- cobalt/iron component is combined with copper or nickel or both in the proportions set forth below.

According to an important feature of this invention, therefore, a magnetic alloy having a field strength many times greater than that which would be expected from iron/cobalt, platinum/iron and even platinum/cobalt alloys, can be obtained by combining in the alloy from 96 to atomic percent of a platinum/cobalt component with 4 to 30 atomic percent of iron and advantageously from 0 to 5 atomic percent nickel and/or 0 to- 5 atomic percent copper. The platinum may be present in an amount of 40 to 60 atomic percent, preferably 45 to 55 atomic percent while cobalt makes up the balance.

The platinum/cobalt component can, moreover, consist essentially of 50% (atomic) platinum and 50% (atomic) cobalt, corresponding to substantially equal amounts of platinum and cobalt atoms in the final alloy. Within the platinum/cobalt component, the limitation of the variation to 1% (atomic) by weight of Pt and Co is found to provide best results. We have found, furthermore, that when nickel is used in the alloy, excellent results are obtained when it is employed along with 0.01 to 5 atomic percent copper. Thus, according to this invention, a platinum/cobalt/iron/nickel copper alloy can be made with up to 5 atomic percent nickel,

up to 5 atomic percent copper, up to 30 atomic percent iron and as little as 60 atomic percent of the platinum/- cobalt component.

On the other hand, the alloy can be free from copper and nickel while containing up to 30 atomic percent iron and up to 70 atomic percent of the platinum/- cobalt component. Platinum/cobalt/nickel alloys can range between compositions containing 99.9 atomic percent of the platinum/cobalt component and iron (at least 4 atomic percent) and 0.1 atomic percent nickel (no copper) to compositions containing 94.9% platinum/cobalt component and at least 4 atomic percent iron, 0.1 atomic percent nickel and 5 atomic percent copper, and to compositions consisting of atomic percent platinum/cobalt component and iron at least 4 atomic percent, 5 atomic percent nickel and 5 atomic I percent copper. An excellent magnetic material consists essentially of 50 atomic percent Pt, 4 to 15 atomic percent iron, 0 to 5 atomic percent Mi, 0 to 5 atomic percent copper and the balance cobalt.

The term atomic percent and those of similar import are used to indicate concentration in the metal alloy lattice in terms of the proportions of atoms rather than weight proportions. The atomic percent is, of course, proportional to the value of the weight concentration (percent by weight) divided by the atomic weight of the substance; thus, atomic percent by weight/atomic weight.

According to a further feature of this invention, the proportion of iron should be approximately ten times greater than the proportion of nickel present in the alloy and indeed it has been found that best results are obtained with alloys of this type wherein the proportion of copper is about one-tenth that of the nickel.

In a nickel/iron containing composition of the type constituting the present invention, the platinum/cobalt compomponent can consist of 94.4 atomic percent of the platnium/cobalt component (say, 50 atomic percent platinum and 50 atomic percent cobalt or about 77% by weight platinum and about 23% by weight cobalt), 5 atomic percent iron, 0.5 atomic percent nickel and 0.05 atomic percent copper. (Trace amounts of the usual impurities which do not affect magnetic properties may also be present along with residual quantities of deoxidation or desulfurization metals). These metals are manganese, aluminum and titanium; up to 0.1 to 5% by weight in total of the desulfurization and deoxidation agent, added to the powdered alloying metals prior to melting to form the alloy, gives good results.

According to another feature of this invention, the alloys are cast and then heat-treated at an elevated temperature from 900C to 1,400C, preferably between l,000C and 1,200C, for a period in excess of one hour. After this initial treatment, the body is swaged preferably to rod or needle-shape in from 2 to 5 stages to a diameter of approximately one fourth the diameter of the cast body and a cross-section of about one sixteenth. This swaging step is followed by a further heat treatment at the aforementioned elevated temperatures for a period of between 15 minutes and 2 hours and preferably about A hour, the body then being cooled in steps of 200C to 300C in intervals of from 5 to 20 minutes until a temperature in the range of 500C to 800C, preferably 550C to 700C, is attained and, at this temperature, prolonged cooling is advantageous (e.g. to 15 hours).

DESCRIPTION OF THE DRAWING The invention will be described in greater detail below with reference to specific examples and the accompanying drawing in which:

FIGS. 1 and 2 are graphs illustrating the present invention; and

FIGS.. 3 7 are axial cross-sectional views through magnetically operable reed-type relays illustrating typical uses for the magnetic material of the present invention.

SPECIFIC DESCRIPTION In FIG. 1, we show the magnetic properties (plotted along the ordinate in units of 10 gaussoersted of compositions identical to that of Example I but containing varying amounts of nickel (plotted along the abscissa in atomic percent). From this FIGURE, it will be apparent that the properties rise rapidly as the nickel proportion is increased from to 0.5 atomic percent and remains substantially constant through a range of 0.5 to (atomic) before falling off to a material extent. The copper proportion is somewhat more critical as can be seen from FIG. 2 in which a graph of the system of Example II is presented illustrating the effect of various concentrations of copper (plotted along the abscissa in atomic percent). From this graph it is apparent that even traces of copper will improve the magnetic properties and indeed that these properties improve through a copper concentration of trace amounts to atomic percent. Best results have been found with copper concentrations between 0.01 and 5% (atomic), the magnetic properties being more stable at these concentrations.

In FIG. 3, we show an embodiment of a reed-type switch or relay in which one contact is ormed by a bar 4 of the magnetic material made as described in Examples I and II and magnetized by conventional techniques so as to have a north-magnetic pole 4n at the free end of the bar and a south-magnetic pole 4s at the end of the bar 4 connected to a flexible-reed terminal 2. The latter extends at 2a from the hermetically sealed evacuated glass tube 1, while a magnetically permeable (e.g. iron) body 5 is disposed proximal to the northmagnetic pole 4n upon a flexible magnetizable reed 3 to which the magnetically permeable rod 5 is attached.

When an electric current is passed through the coil 6 in one sense, the free end of the bar 5 is temporarily magnetized to a south-magnetic polarity and the free ends of the

bars

4 and 5 are drawn together by attractive magnetic forces and a circuit is closed through the switch of FIG. 3. When the current flow through the coil is terminated, the permanent-magnet force of bar 4 is sufficient to retain the bar 5 in the closed condition of the switch. Upon reversal of the current flow through the coil 6, the polarity at the free end of bar 5 is reversed (e.g. changes to north) so that repulsive forces separate the contact and open-circuit the switch. Since the bar 4 is composed in major part of platinum and cobalt (see Example I or II), it also sets as a corrosion-and-pitting-resistant contact material and has little tendency to spark.

In FIG. 4, we show a modification of the system of FIG. 3 wherein neither of the magnetizable contacts 104 and within the hermetically sealed evacuated glass capsule 10 is permanently magnetic. In this case, the reed-

type terminals

102 and 103 extending longitudinally into the glass tube 101 are composed of magnetically permeable material and are respectively surrounded by energization of de-energization coils 106', 106".

These coils may respectively be make and break coils operable by controlled circuits represented at C and C, respectively, while the

terminals

102 and 103 are connected between a source S and its load L. The coil 106' is so poled as to magnetize the contact 104 which, like the contact 105, is composed of the magnetic material of Example I or Example ll.

When the coil 106" is energized simultaneously to impart opposite magnetic polarity to the free end of contact 105, the magnetic attractive forces close the contact and complete the circuit.

When the coils are de-energized without polarity reversal, sufficient magnetic remanence may hold the circuit closed until one or the other of the coils is energized to produce a repulsive force. In this case, the switch can act as a memory in the manner of a bistable electronic device. More generally, however, the magnetic energization of the

contacts

104 and 105 will be each insufficient to impart sufficient residual magnetic force to keep the contacts closed and upon deenergization of one or both coils, the contacts will spring apart under the resilience of the respective reeds.

In the modification of FIG. 5, the glass tube 201 surrounds a permanently magnetized contact 212 whose ergized to opposite magnetic polarities by the oppositely would coils 206 and 206" which are here shown to be connected in series. When the control signal is a rapid train of signals, the

contacts

204 and 205 will be alternately make and break electrical connections with the contact 212. Should the signal cease while one of the

contacts

204, 205 is engaged with the permanent magnetic contact 212, the magnetic field of the latter will retain the contacts in closed circuit until a reverse polarity is applied.

In the modification of FIG. 6, a single coil 306 energizes a pair of reed contacts 302 and 303 whose magnetically

permeable contact bodies

304 and 305 are respectively engageable with opposite magnetic poles of a U-shaped or horseshoe magnetic contact 312. The latter is carried out by a reed 309 extending into the glass tube 301. When the coil 306 is energized, therefore, one of the

contacts

304, 305 will receive a polarity identical to that of the respective pole of the permanent magnet 312 and be repelled while the other is attracted. Reversal of the current flow through the coil 305 will release the previously attracted

contact

304, 305 and make contact with the other. The system of FIG. 7 provides a pair of permanently

magnetic contacts

404 and 405 whose

reeds

402 and 403 extend into the glass tube 401 in the manner previously described. In this case, the countercontact 412 is magnetically permeable but not permanently magnetic and is carried by the magnetically permeable reed 409 which is surrounded by the energizing coil 406. In the embodiments of FIGS. 3 7, the permanently magnetized and magnetically permeable bodies may each be composed of the material described in connection with Example I and II.

Alternatively, it is possible to use, as to magnetically permeable contact body in a reed-type switch illustrated in FIGS. 3 7, i.e. indicated as numerals 5; 104, 105; 204, 205; 304, 305; 404, 405, a semi-hard magnet, i.e. having a high residual fiux density and relatively low coercive force.

SPECIFIC EXAMPLES EXAMPLE I The magnetic alloy contained (excluding traces of impurities which did not affect the magnetic properties) approximately 5 atomic percent iron, 0.5 atomic percent nickel, the balance platinum and cobalt in equal amounts (i.e. the platinum/cobalt component being composed of 50 atomic platinum and 50 atomic & cobalt); this component is present in substantially 94.5 atomic percent. The alloy was prepared by dissolving or melting an admixture of platinum, cobalt, iron and nickel powders in the above atomic proportions, in a magnesia crusible by high-frequency induction heating in an inert atmosphere (argon) for limiting oxidation of the admixture being dissolved.

Prior to melting, we incorporate into the admixture about 0.1 to 5% by weight of an additive consisting of equal parts by weight of manganese aluminum and titanium powders as a deoxidizing and de-sulfurizing agent; when such agent is omitted cobalt and iron form oxides and sulfides thereof at boundaries of the powders, and these oxides and sulfides detrimentally the machinability of the resultant alloy as well as the magnetic properties thereof.

The alloy contained 5 atomic percent iron, 0.5 atomic percent nickel, the balance platinum and cobalt in equal amounts (i.e. the platinum/cobalt component being composed of 50 atomic platinum and 50 atomic cobalt, 121%) and present in substantially 94.5 atomic percent. The alloy is cast into rods having a diameter of 8 mm, the rods being heat-treated at a temperature of l,000C to 1,200C for 2 hours to disorderization of the alloy lattice. Thereafter, the rods are swaged to a circular diameter of 2 mm in four steps of 6, 4, 3 and 2 mm diameter respectively, each of these steps except the last being floowed by heat-treatment at this temperature for a period of A hour. After the final swaging step, the rods are held at a temperature between l,000C and 800C for 20 minutes. Thereafter, the rods are brought to a reduced temperature of 600C to 700C for 5 minutes and, after (or without) a water-cooling treatment, are maintained at an aging temperature between 500 and 700C for 5 hours for reorderization of the alloy lattice. Note: the maximum in the order-disorder transition curve of the platinum/- cobalt component alloy of the super-lattice type lies at 50 atomic percent and 825C.) The rods showed a maximum energy product (BsH) max. 13.5 X 10 gaussoersted.

EXAMPLE II An alloy was prepared in which 0.5 atomic percent copper, 0.5 atomic percent nickel, 5 atomic percent iron, the balance a platinum/cobalt component as described in Example I and the usual impurities in trace amounts, by the method of this example, and are cast into rods or needles of 8 mm diameter. The rods were heat-treated at a temperature of 1,000C to l,200C for 2 hours to disorderization of the alloy lattice. Thereafter, the rods are swaged to a circular diameter of 2 mm in four steps of 6, 4, 3 and 2 mm diameter respectively, each of these steps except the last being followed by heat-treatment at this temperature for a period of k hour. After the final swaging step, the rods are held at a temperature between 1,000C and 800C for 20 minutes. Thereafter the rods are brought to a reduced temperature of 600C to 700C for 5 minutes. After aging at a temperature of 550C to 700C over a period of 5 hours, the magnetic-energy product BXH (max) of the needles was evaluated and found to be 14.8 X 10 6 gauss-oersted.

EXAMPLE III The semi-hard magnet composed of Pt/Co, Pt/Co/Fe, Pt/Co/Fe/Ni or Pt/Co/Fe/Ni/Cu in the proportions described above can be produced as follows:

The alloy is formed and cast as described in Example I into a body, which is heated to a temperature of about 830C to 1,200C to disorder of the alloy lattice; thereafter the body is rapidly cooled to the aging temperature of about 550C to 750C and maintained at this temperature for about 20 to 400 minutes for ordering of the alloy lattice.

The resulting body, depending on the length of the aging treatment has a residual flux density of about 6,000 to 7,500 gauss and a caercive force of about 20 to 1,000 oersted.

EXAMPLE IV Alloys containing 50 atomic percent platinum, varying amounts of iron (4 to 30 atomic percent iron, preferably 4 to 15 to 20 atomic percent), varying amounts of nickel (i.e. 0 to 5 atomic percent nickel) and as the balance cobalt were prepared. In each preparation, a mixture of these powders in a total quantity of 40 grams was melted by high-frequency induction heating in an argon atmosphere and after incorporating 0.1% by weight manganese serving as a deoxidation and desulfurization agent and cast into a mold having a diameter of 6 mm.

The ingot, after annealing a temperature above the disorder-order transition of the alloy (i.e. at a temperature generally in a range between 900C and 1,400C), was swaged and drawn. These annealing and cold working operation were repeated alternately until the body was reduced in diameter to 2.5 mm. Then the body was cut into lengths of 20 mm.

The body was then subjected to a heat treatment in an evacuated chamber at a temperature of 1,300C (generally between 900C and 1,400C) for 2 hours (generally up to 1 hour). This heat treatment was intended to primarily effect solid-state solvolyzation of the alloy or dissolving alloy constituents so that the iron atoms (and nickel atoms if also present) homogeneously merge in platinum and cobalt phases possibly form iron cobalt and iron platinum (the latter predominating and the former in relatively low proportion) within the platinum-cobalt matrix. Then the alloy was quenched (or otherwise controlledly cooled).

The quenched body was returned to a heat treatment in an argon atmosphere at a temperature of 1,200C (generally between 900C and 1,400C) for 2 hours which purposed accomplishment of disorder reaction and then brought to room temperature; (Note: the post-swaging heat treatment may be eliminated and the swaging, heat-treatment and reheating steps may be interchanged in sequence.)

Finally the alloy was subjected to aging treatment in a temperature range between 500C and 800C (i.e. in the ordering-reaction range of the alloy) to yield the magnetic alloy.

This final stage preferably includes two or more steps. By way of example, the first aging step was at a temperature between 730C and 810C for a period of 10 to 300 seconds followed by quenching to room temperature and the second step was at a temperature between 500C and 600C for a period of 0.5 to 35 hours.

EXAMPLE V With a composition (prepared and treated as outlined above) of 50% Pt, 45% Co and 5% Fe (in atomic proportion) and when aged at a temperature of 750C for 60 seconds in the first step and at 550C for 1 hour in the second step, the alloy showed a maximum energy product 12.1 million Gauss-Oersted with a coercive force 4.9 kilo-oersted and a residual flux density of 7.3 kilo-gauss.

EXAMPLE VI With a composition (prepared and treated as outlined above) of 50% Pt, 42% Co and 8% Fe and when first-aged at 780C for 30 seconds and second-aged at 550C for 1 hour, the alloy showed a maximum energy product of 12.3 MGOe with a coercive force of 4.7 KOe and a residual flux density of 7.5 KG.

EXAMPLE VII With a composition (prepared and treated as outlined above) of 50% Pt, 40% Co and 10% Fe when firstaged at 790C for seconds and second-aged at 550C for 1 hour, the alloy showed a maximum energy product of 12.2 MGOe with a coercive force of 4.2 KOe and a residual flux density of 7.6 KG.

EXAMPLE VIII With a composition (prepared and treated as outlined above) of 50% Pt, 41% Co, 8% Fe and 1% Ni and when first-aged at 780 C for 20 seconds and secondaged at 550C for 1 hour, the alloy showed a maximum energy product of 13.9 MGOe with a coercive force of 5.0 KOe and a residual flux density of 7.7 KG.

EXAMPLE IX With a composition of 50% Pt, 40% Co, 8% Fe and 2% Ni when first-aged at 780C for 20 seconds and second-aged at 550C for 1 hour, the alloy exhibited a maximum energy product of 14.6 MGOe with a coercive force of 5.0 KOe and a residual flux density of 7.9 KG.

EXAMPLE XA EXAMPLE XB With a composition corresponding to that of Example V and consisting of 50 atomic percent platinum, 42 atomic percent cobalt and 8 atomic percent iron, aged in the first step at 780C for 30 seconds and at 550C for 1 hour in the second step, the maximum energy product was 12.3 MGOe, the coercive force was 4.7 K06 and the residual flux density was 7.5 KG.

EXAMPLE XC A composition of 50 atomic percent platinum, 40 atomic percent cobalt and 10 atomic percent iron was prepared as set forth in Example 111 and corresponded to Example V1 thereof. The composition was aged in the first step at 790C for 20 seconds and aged in the second step at 550C for 1 hour. The alloy had a maximum energy product of 12.3 MGOe with a coercive force of 4.2 KOe and a residual flux density of 7.6 KG.

EXAMPLE XD Alloys were made with compositions of 50 atomic percent platinum, 0 to 3 atomic percent iron in 0.5 atomic percent increments and cobalt (balance). The highest maximum energy product obtained was 9.2 MGOe with a coercive force of 4.8 KOe and a residual flux density of 6.4 KG. The improvement found with a minimum of 4% by weight iron as detailed in Examples XA XC above, was a minimum of 20.6%.

EXAMPLE XE When the iron proportion (Example XD) was increased to 4% (atomic) with corresponding decrease of cobalt, the maximum energy product was 11.0 MGOe with a coercive force of 4.9 KOe and residual flux density of 7.0 KG. Abruptly in the region of 4% atomic iron, there appears, therefore, to be a jump in the maximum energy product.

EXAMPLE XF A composition was prepared as described consisting of 50 atomic percent platinum, 35 atomic percent cobait and atomic percent iron. The alloy had a maximum energy product of 12.2 MGOe with a coercive force of 4.2 KOe and a residual flux density of 7.6 KG. This test demonstrated that substantially at the midpoint of the range of iron in the alloy, according to the above-identified application, there is basically no variation in the maximum energy product when the latter is compared with the average of Examples XA XC corresponding to Examples IV VI of the application.

EXAMPLE XG Further increase in the iron proportion showed that beyond approximately 30 atomic percent iron and, more particularly, in the range of 15 atomic percent iron and above, the magnetic energy product falls off sharply to 3 MGOe with a coercive force of 1.6 KOe and a residual flux density of 3.0 KG.

EXAMPLE XH A composition corresponding to Example VII of the aforesaid application was prepared as described in Example III thereof and consisted of 50 atomic percent platinum, 41 atomic percent cobalt, 8 atomic percent iron and 1 atomic percent nickel. First step aging was carried out at 780C for seconds and second step aging was carried out at 550C for 1 hour. The maximum energy product was 13.9 MGOe with a coercive force of 5.0 KOe and a residual flux density of 7.7 KH.

EXAMPLE XI A composition corresponding to that of Example VIII of the patent application was prepared with SOatomic percent platinum, 40 atomic percent cobalt, 8 atomic percent iron and 2 atomic percent nickel. The composition was initially aged at 780C for 20 seconds and subsequently aged at 550C for 1 hour. The maximum energy product was 14.6 MGOe with a coercive force of 5,0 KOe and a residual flux density of 7.9 KG. A comparison of Example XH and XI with Example XB shows that the addition of nickel is able to increase the magnetic energy product over the same system without nickel by approximately 18%.

EXAMPLE XJ Tests were made to show the relationship of inclusion of iron to the effect of nickel in improving the magnetic energy product as described in connection with Examples X11 and XI. With iron inclusions of less than 4% (atomic) and more than 20 atomic percent, no appreciable improvement in the maximum nagnetic energy product was obtained by incorporation of nickel. When the iron proportion was in the range of 4 atomic percent to 15 atomic percent, however, substantial improvement in the maximum magnetic energy product was obtained when nickel was added in the amounts ranging from 0.1 atomic percent to 5 atomic percent in increments of 0.1 atomic percent. The average improvement was between 10 and 25%.

retards the disorder-order transition rate of the alloy to provide superior magnetic properties even under severe heat treatment.

EXAMPLE XL A system was prepared as described in Example I, the rods having a maximum energy product of 13.5 MGOe. The composition of the rods was represented in FIG. 1. It was observed that FIG. 1 is typical with compositions of 4 to 15 atomic percent iron, 0.1 to 5 atomic percent nickel and the maximum, equimolecular platinum/- cobalt. With a composition containing 8 atomic percent iron, 0.1 to 5 atomic percent nickel, balance equimolecular platinum/cobalt, the maximum energy product was at least 13.0 MGOe. With iron compositions below 4%, however, the maximum energy product was found to be generally below 9.5 MGOe while, with iron content above 15%, e.g. about 20 atomic percent, the magnetic energy product falls as low as 30 MGOe. Similar tendencies were observed when copper was added. i

EXAMPLE XI The following Table illustrates further comparison of the alloys of the present invention (marked with an asterisk w1th alloys outside its scope.

TABLE COMPOSITION Atomic Percent MAGNETIC VALUES Pt Co Fe Nl Cu KOe KG MGOe 42 Balance 5 4.9 7.1 11.8 do. do. 8 4.7 7.2 11.9 do. do. 10 4.5 7.3 12.0 do. do. 0-3 4.5 5.8 8.3 do. do. 4 4.7 7.0 I 11.0 do. do. 15 4.0 7.5 12.0 do. do. 30 1.5 3.0 2.0

do. do. 8 1 4.7 7.5 13.0 do. do. 8 2 4.6 7.6 13.4 46 do. 5 5.0 7.2 11.7 do. do. 8 4.9 7.3 12.0 do. do. 10 4.7 7.5 12.3 do. do. 0-3 4.7 6.0 9.0

do. do. 4 4.9 7.1 11.2 do. do. 15 4.1 7.9 12.3 do. do. 30 1.8 3.3 2.9

do. do. 8 1 4.9 7.7 13.8 do. do. 8 2 4.9 7.8 14.0 r 50 45 5 4.9 7.3 12.1 do. 42 8 4.7 7.5 12.3 8 do. 40 10 4.2 7.6 12.2 do. 47-50 0-3 4.8 6.4 9.2

do. 46 4 4.9 7.0 11.0 8 do. 35 15 4.2 7.6 12.2 do. 20 30 1.6 3.0 3.0

do. 41 8 1 5.0 7.7 13.9 do. 40 8 2 5.0 7.9 14.6 52 Balance 5 4.8 7.3 12.0 do. do. 8 4.7 7.5 12.2 do. do. 10 4.6 7.7 12.3 do. do. 0-3 4.3 6.0 8.8

do. do. 4 4.8 7.2 11.8 do. do. 15 4.2 7.5 12.2 do. do. 30 1.5 3.0 2.8

do. do. 8 4.9 7.8 13.9 do. do. 8 2 5.0 7.9 14.3 56 do. 5 4.6 7.2 11.7 do. do. 8 4.5 7.4 11.9 do. do. 10 4.3 7.6 12.2 r

56 Balance O-3 4.1 5.8 8.3

do. do. 4 4.6 7.1 11.6 do. do. 15 4.2 7.7 12.1 do. do. 30 1.4 2.5 2.6

do. do. 8 1 4.9 7.7 13.8 do. do. 8 2 5.1 7.6 14.0

While the magnetic alloys in accordance with the present invention can be prepared in various known ways, the best practice is to follow the combined swaging and heat treatment originally described above which forms a part of the present invention.

We claim:

1. A method of preparing a magnetic material comprising the steps of:

a. mixing 40 to 60 atomic percent platinum, 4 to 15 atomic percent iron, to 5 atomic percent nickel, 0 to 5 atomic percent copper, and the balance to 100 atomic percent cobalt, the cobalt being present in an atomic proportion exceeding that of the iron, with a deoxidation and desulfurization metal selected from the group which consists of manganese, aluminum and titanium, the metal being present in an amount between 0.01 and 5 percent by 12 weight of the mixture;

b. melting said mixture and. casting the melt into a body;

c. heating said body to a temperature between substantially 900C and l,400C and above the latticedisorder transition temperature for a period in excess of 1 hour;

d. thereafter swaging said body to a diameter of approximately one fourth the diameter of the cast body and a cross section of about one sixteenth the cross section of the cast body in two to five stages; and

e. heat treating said body at a temperature ranging between substantially 500C and 800C for a period of at least one hour and sufficient to reorder the lattice.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3,860,458 DATED 14 January 1975 |NV ENTOR(S) Kiyoshi INOUE and Hideo KANEKO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, line 1721, for the assignee's name read:

. Ishifuku Kinzoku Kogyo K.K., (also known as Ishifuku Metal Industry Co.,Ltd.), Tokyo, Japan r d h Engncd and Sea 6 t IS sixth D y of January 1976 [SEAL] Q Arrest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer (ummissinner uj'Patents and Trademarks