The magnetic properties of aluminum-nickel-cobalt change very little with temperature, and it is still widely used in permanent magnet devices with high temperature stability, especially in weapons and equipment such as torpedoes, missiles, and aircraft, and in spacecraft such as satellites. This material has a high residual magnetization density, up to 1.35 T, but its intrinsic coercivity is very low, usually less than 160 kA/m. Its demagnetization curve is nonlinear, and the recovery line does not overlap with the demagnetization curve. Therefore, special attention must be paid to its uniqueness in the design and manufacture of the magnetic circuit of the device. It is necessary to perform stabilization treatment on the permanent magnet in advance. According to the low coercivity of aluminum-nickel-cobalt permanent magnet materials, it is strictly prohibited to contact any ferromagnetic materials during use to avoid local irreversible demagnetization or distortion of the magnetization density distribution. In addition, to strengthen its anti-demagnetization, the magnetic pole surface of aluminum-nickel-cobalt permanent magnet materials is often designed as a long cylindrical or rod shape. In addition, aluminum-nickel-cobalt permanent magnet materials have low mechanical strength, high hardness, and are prone to brittleness, poor machinability, so they cannot be designed as structural components. During processing, only a small amount of grinding or electrical discharge machining can be performed, and forging and other mechanical processing cannot be used.
Alnico permanent magnet materials are the earliest and most widely used type of permanent magnet materials, and their preparation processes and technologies are relatively mature. The following table lists the commonly used grades of Alnico permanent magnet materials produced in China.
Table: Designations of Aluminum-Nickel-Cobalt Permanent Magnet Materials
|
Brand number
|
Br
(T)
|
HcB
(kA/m)
|
(BH")max
kJ/m3")
|
AlphaBr
(%/℃)
|
Mr
|
|
LN10
|
0.60
|
36
|
10
|
-0.022
|
6.0 to 7.0
|
|
LNG13
|
0.68
|
48
|
13
|
6.0 to 6.7
|
|
LNG32
|
1.20
|
44
|
32
|
-0.016
|
3.5~4.8
|
|
LNG32H
|
1.10
|
56
|
32
|
3.2~4.5
|
|
LNGT32
|
0.80
|
100
|
32
|
-0.020
|
2.4~3.6
|
|
LNGT40
|
0.72
|
410
|
40
|
|
LNG52DIV>
|
1.30
|
56
|
52
|
-0.016
|
2.4~3.6
|
|
LNG60
|
1.35
|
60
|
60
|
2.4~3.6
|
|
LNGT56
|
0.95
|
104
|
56
|
-0.02 to -0.025
|
2.4~3.6
|
|
LNGT70
|
greater than 0.90
|
145
|
70
|
|
LNGT72
|
1.05
|
111
|
72
|
0.02 to -0.025
|
2.0~3.2
|
|
LNGT85
|
1.08
|
120
|
85
|
2.0~3.0
|
|
LNGS9
|
0.5
|
35
|
<9
|
6.0 to 6.7
|
|
LNGS25
|
1.05
|
46
|
25
|
3.2~4.3
|
|
LNGTS28
|
0.7
|
95
|
28
|
Note: L represents aluminum, N represents nickel, G represents cobalt, T represents titanium, S represents sintering
The significant feature of aluminum-nickel-cobalt permanent magnet material is:
Temperature coefficient is small, residual magnetism is reversible.AlphaBromineIt is approximately -0.02%/℃ only, and the coercive force reversible temperature coefficient is approximately +0.015%/℃ only.
Excellent corrosion resistance
Curie temperature reaches up to 860 ℃, and the operating temperature can reach 550 ℃.

