Rare earth supermagnetostrictive materials.

Rare earth supermagnetostrictive materials.

Magnetic field can cause the change of the material size and shape, this is the magnetostrictive effect, in the past mainly in nickel metal and other materials that can be observed in the change of the relative scale of 10 to 5, and is widely used in the ultrasonic generator and transducer. But a. e. Clark of the United States in 1974 found that the rare earth - iron compounds have A magnetic strictive value of nearly A hundredfold, which obviously has important application value.

After more than 10 years of efforts, several companies in the United States, Japan and other countries can provide practical (Tb, Dy) Fe2 polycrystalline o rientation rods. By the institute of physics, Chinese academy of sciences in 1976 for the first time in our country in this research, one after another after Beijing iron and steel research institute, Beijing university of science and technology and many other units engaged in the research and development, and set up some company production of rare earths - ferromagnetic striction rods and related products. Especially successful grow, institute of physics, Chinese academy of sciences in 1997, Tb, Dy) Fe2 < 111 > o rientation of single crystal rod, the o rientation is the best o rientation of magnetostrictive, growth is very difficult, but there has been no breakthrough in the world, so the results to the single crystal growth in the international leading level of our country.

In addition, Beijing university of science and technology has also used its own patent to grow the polycrystalline rod of <110> o rientation, which has a direct meaning to the application. This kind of rare earth material will be used in underwater acoustic sonar system, precision machining system, optical fine tuning system, aerospace s hock a bsorber system, important valve and nozzle adjustment system.

In December 2002, Beijing nonferrous metal research institute of rare earth materials developed by the national engineering research center of the new technology of "one-step" (that is, the smelting of directional solidification - heat treatment on one device for completion), was prepared successfully at present, China's largest diameter (70 mm 70 mm diameter, length) of rare earth giant magnetostrictive materials, magnetostrictive strain under low magnetic field, mechanical properties, product consistency, yield and other major technical indicators have reached the international advanced level.

The rare earth magnetostrictive material of terbium, which contains about 60 percent of rare earth metal terbium and dysprosium, is another important breakthrough in the application of rare earth in new materials. In 1989, Edge Technologies began to produce the terfenol-d, a rare earth magnetostrictive material, which can be used to transform the field of electricity (magnetic) - mechanical (sound). Since its inception, the U.S. navy has developed its application in sonar, followed by research and development in Sweden, Japan and other countries. By the year 2000, the production of rare earth magnetostrictive alloy will reach 100 tons, and the total demand of high purity Tb, Dy and Sm will reach 60 tons.

The study of rare earth magnetostrictive materials in our country has made great progress recently, and has entered the market and is practical. The large-sized directional solidified crystals have been successfully prepared, which are applied to the high power sonar of the sea and the three gorges project of the Yangtze river and the land sonar of the xiaolangdi project. Currently, the baotou rare earth institute and other units have developed the successful rare earth magnetostrictive materials (terfenol-d) and have the ability of small batch production.