RE-TM-B alloys, method for their production and permanent magnets containing such alloys

Claim 2

1 . A magnetically hard alloy composition characterised in that it comprises at least about ten atomic percent of one or more rare earth elements including one or both of the elements neodymium and praseodymium; about O.5 to 10 atomic percent boron; and iron; said alloy containing a major portion of a magnetically hard, finely crystalline phase.

Claim 3

A magnetically hard alloy composition according to claim 1, characterised in that the boron in the alloy increases the Curie temperature with respect to a like alloy of otherwise like composition containing substantially no boron.

Claim 4

A magnetically hard alloy composition according to claim 1 or 2, characterised in that the one or more rare earth elements consist predominantly of neodymium, praseodymium or combinations thereof.

Claim 5

A magnetically hard alloy composition according to any one of the preceding claims, characterised in that the alloy composition has the constituent formula RE 1-x (TM 1-y B y ) x where RE is one or more rare earth elements taken from the group consisting of neodymium and praseodymium, TM is one or more transition metal elements taken from the group consisting of iron and mixtures of iron and cobalt where the ratio of iron to cobalt is at least 3:2 and B is the element boron; x is the combined atomic fraction of said transition metal and boron present in said composition and 0.5 x 0.9; and wherein y is the atomic fraction of boron based on the amount of transition metal plus boron in said composition and 0.05 y 0.10.

Claim 6

A magnetically hard alloy composition according to any one of claims 1 to 3, characterised in that the alloy composition has the constituent formula RE 1-x (TM 1-y B y ) x where RE is one or more rare earth elements taken from the group consisting of praseodymium, neodymium, samarium and mischmetals thereof; TM is iron and B is the element boron; x is the combined atomic fraction of said iron and boron present in said alloy and 0.5 x 0.9, and y is the atomic fraction of boron based on the amount of said iron plus boron present in said alloy and 0.01 y 0.10.

Claim 7

A magnetically hard alloy composition characterised in that it is formed by melting a mixture comprising one or more rare earth elements taken from the group consisting of praseodymium, neodymium or mixtures of neodymium with praseodymium, samarium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and mischmetals thereof, and one or more transition metals taken from the group consisting of iron and mixtures of iron with other transition metals; and thereafter cooling said mixture from its molten state at a rate such that the resultant alloy has a finely crystalline microstructure, the intrinsic magnetic coercivity of such alloy being increased at temperatures below the Curie temperature thereof by the addition of boron to said mixture prior to said cooling.

Claim 8

A magnetically hard alloy composition characterised in that it is formed by melting a mixture comprising one or more rare earth elements taken from the group consisting of praseodymium, neodymium or mixtures of neodymium with praseodymium, samarium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and mischmetals thereof, and one or more transition metals taken from the group consisting of iron and mixtures of iron with other transition metals; and thereafter cooling said mixture from its molten state at a rate such that the resultant alloy has a finely crystalline microstructure, the intrinsic magnetic coercivity of such alloy being increased at temperatures below the Curie temperature thereof by the addition of boron to said mixture prior to said cooling.

Claim 9

A magnetically hard alloy composition according to claim 6, characterised in that the magnetic energy product of such cooled alloy is increased at temperatures below the Curie temperature thereof by the presence in said mixture of from about 0.5 to 10.0 atomic percent boron based on the total amount of said rare earth elements and transition metal elements present.

Claim 10

A magnetically hard alloy composition according to claims 6 or 7, characterised in that the atomic ratio of praseodymium and neodymium to the sum of the other said rare earth elements present is greater than 5:1; and the transition metal element present comprises iron or mixtures of iron and cobalt where the atomic ratio of iron to cobalt is greater than 3:2.

Claim 11

A magnetically hard alloy composition according to any one of claims 1 to 8, characterised in that the alloy composition contains at least about 50 atomic percent iron, 0.5 to lO atomic percent boron, and at least 10 atomic percent of one or more rare earth elements taken from the group consisting of neodymium and praseodymium, said alloy including a predominant phase of crystallites having an average diameter less than about 400 nanometers.

Claim 12

A magnetically hard alloy composition according to claim 6 or 7, characterised in that the alloy composition contains at least 10 atomic percent rare earth elements and at least 60 percent of the total rare earth elements consists of praseodymium, neodymium or combinations thereof; from about 0.5 to 10 atomic percent boron; and the balance either iron or a mixture of iron and cobalt wherein the amount of cobalt present comprises less than 40 atomic percent of the mixture.

Claim 13

A magnetically hard alloy composition according to claim 10, characterised in that said composition is characterised by a principal phase of crystallites having an average diameter less than about 400 nanometers.

Claim 14

A magnetically hard alloy composition according to claim 10, characterised in that said composition is characterised by an intrinsic magnetic coercivity of at least 5 kiloOersted and an energy product at magnetic saturation of at least about 10 megaGauss Oersted.

Claim 15

A magnetically hard alloy composition according to claim 10, characterised in that said composition is characterised by a magnetic remanence at saturation of at least 7 kiloGauss.

Claim 16

A magnetically hard alloy composition according to claim 10, characterised in that the transition metal element present is substantially all iron.

Claim 17

A magnetically hard alloy composition according to claim 10, characterised in that the transition metal element present is substantially all iron and the rare earth element present is substantially all neodymium.

Claim 18

A permanent magnet characterised in that it comprises an intermetallic magnetic phase of composition RE 0.12-0.14 (TM 0.93-0.95 B 0.65-0.07 ) 0.86-0.88 where RE is one or more rare earth elements and consists of at least 60 atomic percent of praseodymium and/or neodymium; TM is iron or a mixture of iron and cobalt where the ratio of iron to cobalt is greater than about 3:2, and B is boron.

Claim 19

A permanent magnet characterised in that it comprises an intermetallic magnetic phase of composition RE 0.12-0.14 (TM 0.93-0.95 B 0.65-0.07 ) 0.86-0.88 where RE is one or more rare earth elements and consists of at least 60 atomic percent of praseodymium and/or neodymium; TM is iron or a mixture of iron and cobalt where the ratio of iron to cobalt is greater than about 3:2, and B is boron.

Claim 20

A permanent magnet according to claim 16, characterised in that it comprises an intermetallic magnetic phase of composition Nd 0.12-0.14 (Fe 0.93-0.95 B 0.05-0.07 ) 0.86-0.88.

Claim 21

A permanent magnet according to claim 16, characterised in that it comprises an intermetallic magnetic phase of composition Pr 0.12-0.14 (Fe 0.93-0.95 B 0.05-0.07 ) 0.86-0.88.

Claim 22

A permanent magnet according to claim 16, characterised in that it comprises a body formed of small crystallites generally less than about 400 nanometers in size and consisting essentially of neodymium and/or praseodymium, iron and boron.

Claim 25

A method of making a magnetically hard alloy composition according to claim 21, characterised in that the annealing step is carried out by rapidly heating the solidified alloy to a temperature in the range of 850°K to 1000°K and then rapidly cooling the heated alloy to a temperature below about 500°K.