Method for preparing sintered product, sintered product and magnetostriction material

#The present invention relates to a manufacturing method that yield high density sintered compacts, sintered compacts with high density that can be manufactured according to the manufacturing method, and to magnetostrictive materials with superior magnetostrictive properties and ideal for use on transducers between magnetic energy and mechanical energy.

#When a ferromagnetic compact is magnetized, its dimensions change; this phenomenon is called magnetostriction, and materials that cause this phenomenon are called magnetostrictive materials. The saturation magnetostrictive constant, which is the saturation change amount caused by magnetostriction, generally has the value of 10−5-10−6, and magnetostrictive materials with large saturation magnetostrictive constants are widely used in oscillators, filters and sensors.

#At present, magnetostrictive materials with even larger magnetostriction values are demanded, and among the materials proposed are compounds made of rare earth (R) and iron (Fe). R and Fe form RFe2 Laves-type intermetallic compounds, and although the magnetostriction value of RFe2 Laves-type intermetallic compounds is large when the external magnetic field is large, it is insufficient when the external magnetic field is small. Consequently, a magnetostrictive material having an even larger magnetostriction value is in demand among RFe2 Laves-type intermetallic compounds.

#FIG. 1 is an x-ray diffraction graph of a plane parallel to a direction in which a magnetostrictive material in accordance with the present invention is formed by compaction in magnetic field.

#FIG. 2 is an x-ray diffraction graph of a plane perpendicular to a direction in which the magnetostrictive material in accordance with the present invention is formed by compaction in a magnetic field.

#FIG. 3 is a graph indicating the relationship between the ratio of x-ray diffraction intensity on a (222) plane to that on a (311) plane, and the magnetostriction value, in the parallel direction and the vertical direction.

#Embodiments of the present invention are described in detail below.

#A first method for manufacturing sintered compacts in accordance with an embodiment of the present invention involves sintering alloy powders having a composition represented by Expression 1: RTw (where R is one or more types of rare earth metals, T is one or more types of transition metals, and w is 1<w<4).

#Here, R represents one or more types of rare earth metals selected from among lanthanoid series and actinoid series, and Y. Of these, rare earth metals Nd, Pr, Sm, Tb, Dy and Ho are preferable as R, and Tb and Dy are particularly preferable. This is due to the fact that each of the RT2 Laves-type intermetallic compounds formed by Tb and/or Dy has a high Curie temperature and a large magnetostriction value. In addition, R may be a mixture of these rare earth metals.