JP3706698B2 - SmFe magnetostrictive material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an SmFe-based magnetostrictive material.
[0002]
[Prior art]
Conventionally, as this type of magnetostrictive material, a material composed of an SmFe ₂ alloy (the unit of numerical values is the number of moles of atoms) is known.
[0003]
[Problems to be solved by the invention]
However, the conventional SmFe-based magnetostrictive material has a problem that the amount of magnetostriction in a high temperature region near 50 to 100 ° C. is small.
[0004]
[Means for Solving the Problems]
An object of the present invention is to provide the SmFe-based magnetostrictive material capable of increasing the amount of magnetostriction in the high temperature region.
[0005]
In order to achieve the above object, according to the present invention, it is represented by the general formula: Sm (Fe _1-x Co _x ) ₂ (where x is an atomic ratio), and x is 0.05 ≦ x ≦ 0.1. An SmFe-based magnetostrictive material is provided.
[0006]
The above general formula means that a part of Fe in the SmFe ₂ alloy is replaced with Co. Thus, when Fe is substituted in the range of x ≦ 0.1 by Co having a Curie point higher than that of Fe (Cu Curie point: 1043K, Co Curie point: 1388K), the magnetic moment is reduced in the high temperature region. Therefore, the SmFe-based magnetostrictive material has a relatively large magnetostriction amount in the high temperature region.
[0007]
In the Sm (Fe _1-x Co _x ) ₂ alloy, the ion radius of Co ³⁺ substituted with Fe ³⁺ is 0.65Å, which is smaller than the ion radius of Fe ³⁺ 0.67０．６. Strain is generated in the crystal lattice of the alloy, which can improve the tensile strength of the SmFe-based magnetostrictive material. This is effective in compensating for the weakness of the SmFe-based magnetostrictive material because there are a large number of holes.
[0008]
If such an SmFe-based magnetostrictive material is used as a constituent material of an engine fuel injection actuator, the fuel increase correction in the high temperature region can be performed without an external control means, and the durability of the actuator can be improved. Can be improved.
[0009]
However, when x is greater than 0.1, the change in magnetostriction amount of the SmFe-based magnetostrictive material with respect to temperature change becomes too large in the high temperature region, which is not practical.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Each component was blended so that the final composition was x = 0.1 in the general formula: Sm (Fe _1-x Co _x ) ₂ , that is, Sm (Fe _0.9 Co _0.1 ) ₂ , to obtain a raw material. Next, the raw material was melted in an Ar atmosphere and under reduced pressure (600 Torr) using a high-frequency melting furnace, and then the molten metal was poured into a copper mold at a casting temperature of 1200 ° C. to obtain Example 1 of SmFe-based magnetostrictive material. It was.
[0011]
In the same manner, x = 0.05, i.e. the composition is Sm (Fe _0.95 Co _{0.05) 2} Examples of SmFe-based magnetostrictive material 2 and x = 0.03, i.e. the composition is Sm (Fe _0.97 Co _0.03) example 3 and x = 0 of SmFe-based magnetostrictive material is _2, i.e. the composition was obtained example 4 of SmFe-based magnetostrictive material is SmFe _2.
[0012]
Next, heat treatment was performed on Examples 1 to 4 in a vacuum at 800 ° C. for 6 hours followed by furnace cooling to improve the magnetostrictive performance. In this case, the rate of temperature increase from room temperature (about 25 ° C.) to 800 ° C. was set to 517 ° C./h.
[0013]
FIG. 1 shows the relationship between the Co content and the lattice constant in Examples 1 to 4. 1 that the lattice constants of Examples 1 to 3 containing Co are smaller than those of Example 4 not containing Co.
[0014]
FIG. 2 is a photomicrograph showing the metal structure of Example 1. In FIG. 2, the white main portion is made of Sm (Fe _0.9 Co _0.1 ) ₂ , and the black and gray portions are pores. In the white main part, it can be seen that Co does not appear and is therefore completely dissolved.
[0015]
Next, the magnetostriction amount of Examples 1 to 4 was measured. The amount of magnetostriction was measured using strain gauges and holding Examples 1 to 4 at temperatures of −40, 0, 20, 60, and 120 ° C. and applying a magnetic field of 1.5 kOe to them. Then, when the magnetostriction amount of Example 4 at a temperature of 20 ° C. was set to “1”, the relative magnetostriction amount at each temperature of Examples 1 to 4 was obtained, and the result of FIG. 3 was obtained.
[0016]
As is clear from FIG. 3, in the high temperature region near 50 to 100 ° C., the relative magnetostriction amount of Example 4 that does not contain Co is the smallest, and the relative magnetostriction amount increases in the order of Examples 3 to 1 as the Co content increases. It can be seen that it is larger than that of Example 4. In the case of Example 1, the amount of relative magnetostriction increases as the temperature rises. In the case of Example 2, the amount of relative magnetostriction becomes substantially constant regardless of the temperature rise. In Example 3, the amount of relative magnetostriction decreases as the temperature rises. Tend to be. Therefore, in the present invention, the lower limit of x, shall be the x ≧ 0.05.
[0017]
【The invention's effect】
According to the present invention, by configuring as described above, it is possible to provide an SmFe-based magnetostrictive material having a relatively large magnetostriction amount in a high temperature region. This material can be used for actuators, sensors, etc. used in the high temperature region. It is effective as a constituent material.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between Co content and lattice constant.
2 is a photomicrograph showing the metal structure of Example 1. FIG.
FIG. 3 is a graph showing the relationship between test temperature and relative magnetostriction.

Claims (1)

A SmFe-based magnetostrictive material represented by a general formula: Sm (Fe _1-x Co _x ) ₂ (where x is an atomic ratio), wherein x is 0.05 ≦ x ≦ 0.1.

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