Method for producing nanocomposite magnet using atomizing method
View Patent ↗A rare-earth alloy powder is obtained by rapidly cooling a melt of an alloy by an atomization process. The alloy has a composition represented by (Fe 1-m T m ) 100-x-y-z Q x R y Ti z M n , where T is at least one of Co and Ni, Q is at least one of B and C, R is at least one of the rare-earth metal elements and yttrium, and M is at least one of Nb, Zr, Mo, Ta and Hf. The mole fractions x, y, z, m and n satisfy 10 at %<x≦25 at %, 6 at %≦y<10 at %, 0.1 at %≦z≦12 at %, 0≦m≦0.5, and 0 at %≦n≦10 at %, respectively. By adding Ti to the alloy, the nucleation and growth of α-Fe during the rapid quenching process can be minimized.
1. A nanocomposite magnet powder of an iron-based rare-earth alloy having a composition represented by the general formula:
(Fe 1-m T m ) 100-x-y-z-n Q x R y Ti z M n (where T is at least one element selected from the group consisting of Co and Ni; Q is at least one element selected from the group consisting of B and C; R is at least one element selected from the group consisting of the rare-earth metal elements and yttrium; and M is at least one element selected from the group consisting of Nb, Zr, Mo, Ta and Hf), the mole fractions x, y, z, m and n satisfying the inequalities of:
10 at %<x≦25 at %;
6 at %≦y<10 at %;
0.1 at %≦z≦12 at %;
0≦m≦0.5; and
0 at %≦n≦10 at %, respectively,
wherein the nanocomposite magnet powder is obtained by an atomization process and includes at least two types of ferromagnetic crystalline phases, in which an R 2 Fe 14 B type compound phase serving as a hard magnetic phase has an average grain size of 10 nm to 200 nm and a soft magnetic phase has an average grain size of 1 nm to 50 nm;
a ferromagnetic iron-based boride phase and an α-Fe phase serving as the soft magnetic phase are present on a grain boundary or sub-boundary of the R 2 Fe 14 B type compound phase; and
the average crystal grain size of the ferromagnetic iron-based boride phase and α-Fe is smaller than that of the R 2 Fe 14 B type compound phase.
2. The iron-based rare-earth alloy nanocomposite magnet powder of claim 1 , wherein the R 2 Fe 14 B type compound phase, the boride phase and the α-Fe phase are present in the same metal structure.
3. The iron-based rare-earth alloy nanocomposite magnet powder of claim 1 , wherein the iron-based boride includes Fe 3 B and/or Fe 23 B 6 .
4. The iron-based rare-earth alloy nanocomposite magnet powder of claim 1 , wherein the magnet powder has a mean particle size of 1 μm to 100 μm.
5. The iron-based rare-earth alloy nanocomposite magnet powder of claim 1 , wherein the magnet powder exhibits hard magnetic properties including a coercivity H cj ≧480 kA/m and a remanence B r ≧0.6 T.
6. A bonded magnet comprising the iron-based rare-earth alloy nanocomposite magnet powder of claim 1 .
7. A method of making an iron-based rare-earth alloy nanocomposite magnet powder, the method comprising the steps of:
obtaining a rare-earth alloy magnet powder by rapidly cooling a melt of an alloy by an atomization process, the alloy having a composition represented by the general formula: (Fe 1-m T m ) 100-x-y-z-n Q x R y Ti z M n (where T is at least one element selected from the group consisting of Co and Ni; Q is at least one element selected from the group consisting of B and C; R is at least one element selected from the group consisting of the rare-earth metal elements and yttrium; and M is at least one element selected from the group consisting of Nb, Zr, Mo, Ta and Hf), the mole fractions x, y, z, m and n satisfying the inequalities of:
10 at %<x≦25 at %;
6 at %≦y<10 at %;
0.1 at %≦z≦12 at %;
0≦m≦0.5, and
0 at %≦n≦10 at %, respectively; and
thermally treating the magnet powder, thereby forming a structure that includes at least two types of ferromagnetic crystalline phases, in which an R 2 Fe 14 B type compound phase serving as a hard magnetic phase has an average grain size of 10 nm to 200 nm and a soft magnetic phase has an average grain size of 1 nm to 50 nm; wherein
a ferromagnetic iron-based boride phase and an α-Fe phase serving as the soft magnetic phase are present on a grain boundary or sub-boundary of the R 2 Fe 14 B type compound phase; and
the average crystal grain size of the ferromagnetic iron-based boride phase and α-Fe is smaller than that of the R 2 Fe 14 B type compound phase.
8. The method of claim 7 , wherein the step of rapidly cooling the melt by the atomization process results in making a rapidly solidified alloy including at least 60 vol % of the R 2 Fe 14 B type compound phase.
9. The method of claim 7 , wherein the iron-based boride includes Fe 3 B and/or Fe 23 B6.
10. A method for producing a bonded magnet, the method comprising the steps of:
preparing an iron-based rare-earth alloy nanocomposite magnet powder by the method claim 7 , and
processing the magnet powder into the bonded magnet.