Study On New Sintering Method, Structure And Properties Of Rare-Earth Magnetostrictive Materials

In this paper, a new sintering method is exploited to fabricate Terfenol-D sintered compacts. Besides, the rare-earth giant magnetostrictive materials have been fabricated in an arc-melting furnace, and the structure, magnetic properties and magnetostriction have been investigated.A new sintering method, which is called low-temperature instantaneous liquid-phase sintering with addition of Sn, was exploited to fabricate Terfenol-D sintered compacts. In this work, the influences of powder size, Sn content, compaction pressure, and sintering technique on the magnetic (including magnetostrictive) and mechanical properties have been investigated. It is found that the sintered compacts fabricated by this means possess higher oxidation resistance and the hard brittleness improves. The compacts fabricated with the finest Terfenol-D powder mixed with Sn powder obtain the highest magnetostrictive property. The optimum Sn content is in the range between 8:100 and 10:100. But it is hard to determine the optimum compaction pressure, because the magnetostrictive property deteriorates while the mechanical property improves with the increase of the compaction pressure. The RTP is more suitable for sintering this material than the common resistance furnace. The large magnetostriction of 546 ppm at 12 kOe is obtained for the sintered compact fabricated at the following conditions: powder size <75μm, a Sn content of 8:100, a compaction pressure of 1.0 GPa, and sintering at 250℃ for 150 seconds in RTP.Study on (Pr_0.15Tb_0.3Dy_0.55(FeM)_1.85 (M=Ge, Cu, Co) alloys shows the effect of M substitution for Fe. The substitution of Ge for Fe makes lattice parameter and magnetostrictiondecrease, and the Ge content should no more than 0.2. With the increase of Cu content, the magnetostriction and saturation magnetization decrease, and the Cu content should be limited in 0.25 otherwise RFe3 phase will appear. With the increase of Cu content, the lattice parameter decreases when 0^x^0.1, and increase then decrease when 0.1 ^x^0.25. The introduction of Co induces saturation magnetization decrease, and all samples are entirely MgCu2-type cubic Laves phase when x^0.4. With the increase of Co content, the lattice parameter decreases first when 0^x^0.2, and increase then decrease when 0.2^x^0.4. And low decrease of lattice parameter deteriorates the magnetostriction, while high decrease increases the magnetostriction.