Method of making Nd—Fe—B magnetic materials with reduced heavy rare earth metals
A method of making a magnetic material includes a step of providing a first material in the form of a core powder containing Nd, Fe and B. The first material is combined with the second material to form a powder combination. The second material includes a component selected from the group consisting of Dy, Tb, and combinations thereof. The powder combination is encapsulated to form an encapsulated powder combination. A magnetic field is applied to the powder combination during encapsulation and thereafter to align the magnetic dipoles therein. The encapsulated powder combination is isostatically pressed with heat to form the magnetic material.
1. A method of making a magnetic material, the method comprising:
a) providing a first material including a core powder containing Nd, Fe and B;
b) combining the first material with a second material to form a powder combination, the second material comprising a component selected from the group consisting of Dy, Tb, and combinations thereof;
c) encapsulating the powder combination to form an encapsulated powder combination by selectively laser sintering the powder combination to form a solid skin defining a predetermined pattern;
d) applying a magnetic field during encapsulating and thereafter to the powder combination to impart magnetization thereto; and
e) isostatically pressing the encapsulated powder combination while heating such that the temperature of the powder combination increases from a first temperature to a second temperature to form a pressed composition.
2. The method of claim 1 further comprising:
f) heating and sintering the pressed composition at a temperature from about 500 to 1000° C.
3. The method of claim 1 further comprising subsequent annealing to further stabilize microstructures in the pressed composition and optimize magnetic properties of the pressed composition.
4. The method of claim 3 wherein the annealing includes heating the pressed composition at stepped temperatures from a high temperature to a low temperature.
5. The method of claim 1 wherein the step of isostatically pressing the encapsulated powder combination includes pressing the powder combination with an inert gas at pressures from 50 MPa to 350 MPa.
6. The method of claim 1 wherein the first temperature is from about 5° C. to about 35° C. and the second temperature is from about 500° C. to about 1000° C.
7. The method of claim 5 wherein the inert gas is argon or nitrogen.
8. The method of claim 1 wherein the powder combination includes a coating of the second material disposed over the first material.
9. The method of claim 8 wherein the coating includes dysprosium, terbium, or combinations thereof.
10. The method of claim 8 wherein the pressed composition includes a non-uniform distribution of Dy, Tb, or combinations thereof.
11. The method of claim 1 wherein the powder combination includes Dy in an average concentration from about 0.3 to about 6 weight percent.
12. The method of claim 1 wherein the powder combination includes Tb in an average concentration from about zero to about 3 weight percent.
13. The method of claim 1 wherein the magnetic field has a magnetic field strength from about 1 to about 3 Tesla (T).
14. The method of claim 1 wherein the first material is described by formula Nd 2 Fe 14 B.
15. The method of claim 14 wherein the first material further includes a component selected from the group consisting of Pr, Ga, Co, Cu, and combinations thereof.
16. The method of claim 1 wherein the second material comprises from about 5 to about 95 weight percent dysprosium and 95 to 5 weight percent terbium.
17. The method of claim 16 wherein the second material further includes a component selected from the group consisting of Fe, B, Pr, Ga, B, Co, Cu, and combinations thereof.
18. A method of making a magnetic material, the method comprising:
a) providing a core powder containing Nd, Fe and B;
b) combining the core powder with a rare earth metal-containing powder to form a powder combination;
c) encapsulating the powder combination to form an encapsulated powder combination by selective laser sintering the powder combination to form a solid skin defining a predetermined pattern;
d) applying a magnetic field to the powder combination to impart magnetization thereto;
e) isostatically pressing the encapsulated powder combination with an inert gas at pressures from 50 MPa to 350 MPa, the encapsulated powder combination being heated such that the temperature of the powder combination increases from a first temperature of about 5° C. to 35° C. to a second temperature of about 500° C. to 1000° C. to form a pressed composition; and
f) heating and sintering the pressed composition at a temperature from about 500 to 1000° C.
19. The method of claim 18 wherein the rare earth metal-containing powder includes a component selected from the group consisting of dysprosium, terbium, and combinations thereof.
20. The method of claim 18 further comprising subsequent annealing to further stabilize microstructures in the pressed composition and optimize magnetic properties of the pressed composition.
21. The method of claim 18 wherein the annealing includes heating the pressed composition at stepped temperatures, a high temperature to a low temperature.