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Permanent magnets:
materials, processing & applications
Paul McGuiness
Department for Nanostructured Materials
Jožef Stefan Institute, Ljubljana, Slovenia
FMF – 19 Apr. 2010
Introduction
• Permanent-magnet (PM) materials
• Magnetic properties
• PM applications
• Nano melt-spun magnets
• Nano HDDR magnets
H2
• Summary
FMF – 19 Apr. 2010
FMF – 19 Apr. 2010
Magnetic properties
Permanent-magnet
properties
Br
Hci
-H
Hcb
Ms
BH
max
+H
FMF – 19 Apr. 2010
280 years of progress
lodestone
(1724)
neodymium
iron boron
(2006)
ferrite
(1950)
FMF – 19 Apr. 2010
How strong?
Sintered Nd-Fe-B
Holding magnets
FMF – 19 Apr. 2010
Improved properties over time
50 MGOe
NdFeB
Sm2Co17
+ price
+ mechanical
+ temperature
+ history
Sm2Fe17N3
SmCo5
AlNiCo
steel
Ferrite
1900
1950
2000
FMF – 19 Apr. 2010
Improved properties over time
1.4
Sintered NdFeB
1.2
1.0
Bonded nano
HDDR NdFeB
Alnicos
0.8
Br (Tesla)
Bonded SmCo
0.6
0.4
(Bonded nano MQ NdFeB)
Sintered Ferrite
0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Hcj (MA/m)
FMF – 19 Apr. 2010
Automotive apps
2008 Lexus RX Hybrid
1118 magnets (inc. 1.9kg of Nd-Fe-B)
1998 Toyota Celica GT
has 543 magnets
1987 Yugo 45 (GV)
has 9 magnets
FMF – 19 Apr. 2010
Computer apps
Fujitsu 1TB 2.5" SATA Hard Disk Drive
FMF – 19 Apr. 2010
Other apps
Alnico magnet – almost zero temp dependence of peroperties
FMF – 19 Apr. 2010
Who makes RE-TM magnets?
1986
2006
China
10%
Europe
2%
US
24%
Japan
41%
US
0%
Japan
20%
Europe
25%
China
78%
1996
US
11%
China
42%
Europe
9%
Japan
38%
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type materials
Nd15Fe77B8 - the magnet
Nd15Fe77B8 - the cast alloy
50 micron
50 micron
NdFe4B4
Nd2Fe14B
Nd2Fe14B
Nd-rich
Nd-rich
Nd2Fe14B
Ms = 1.6 Tesla
Ha = 5 MA/m
Tc = 320°C
Nd-rich phase
MP = ~630°C
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type materials
Attritor
milling
Casting
Align
+ press
HDDR process
Melt spinning
Vacuum sintering
Ribbons
Powder
Sintered magnets
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type materials
Factors that affect remanence:
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by melt spinning
NdFeB
alloy
melt-spinning
as-spun ribbons
Melt spinner
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by melt spinning
NdFeB
alloy
Melt spinner
die-upset magnet
(aniso)
~600 deg C
Over-quenched
amorphous ribbons
crystalline
ribbons
hot-pressed magnet
(iso)
bonded magnet
(iso)
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by melt spinning
Die upset
(fully dense
anisotropic)
Hot pressed
(fully dense
isotropic)
Injection moulded
(not fully dense
isotropic)
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by melt spinning
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by HDDR process
Nd-rich
Nd-hydride
Nd2Fe14B
H2
NdH2
+ Fe
+Fe2B
750 degC
Isotropic and
anisotropic forms
are possible with
small additions of
Zr and Ga
Nd2Fe14B
vac
650 degC
FMF – 19 Apr. 2010
Processing Nd15Fe77B8-type by HDDR process
10 microns
Anisotropic structure that can
be aligned to produce
anisotropic bonded magnets
FMF – 19 Apr. 2010
Properties of NdFeB magnets
iso HDDR bonded
1T
iso melt-spun
hot pressed
magnetisation
aniso melt-spun die upset
anisotropic
sintered
iso melt-spun injec
mould
iso HDDR injec mould
coercivity
1000 kA/m
FMF – 19 Apr. 2010
Summary
• RE-TM magnets have a wide range of applications
• Properties depend on materials and processing
• A nano grain size and good microstructure is vital for good properties
• Good properties can be achieved with a range of techniques
FMF – 19 Apr. 2010
FMF – 19 Apr. 2010