Permanent mechanical alloying

Whereas mechanical alloying of Nd-Fe-B permanent magnets developed from amorphization studies in the Fe-Zr-B system without involving any amorphiz-ation, it will be shown in this section that amorphization by mechanical alloying is essential in the formation of new Sm-Fe-X phases, which show a high potential as novel generation of permanent magnets [3.80]. 

Jinl] Jin, S., Mahajan, S., Brasen, D., Mechanical-Properties of Fe-Cr-Co Ductile Permanent-Magnet Alloys , Metall Trans. A, llA(l), 69-76 (1980) (Experimental, Meehan. Prop., 37)... 

The application of mechanical alloying to the synthesis of rare-earth permanent magnets was first demonstrated by the work of Schultz and co-workers (Schultz et al. 1987). Subsequently, the magnetic properties of a number of rare-earth-transition-metal compounds synthesized by the mechanical alloying of elemental powders, mechanical milling of intermetallic compounds, or by mechanochemical reaction, using oxide and halide precursors, have been studied. 

Magnetic properties of mechanically alloyed rare earth permanent magnet alloys... 

As shown by the studies on rare-earth permanent magnets, the non-equilibrium structures developed by mechanical alloying, with or without subsequent heat treatment, exhibit unique properties. There is thus much potential for the development of new mechanically alloyed materials for applications such as catalysts, electrodes, hydrogen-storage containers and other applications, where property improvements are associated with the amorphous and nanocrystalline structures developed by mechanical alloying. 

The use of mechanical alloying as a processing technique to prepare amorphous, nanocrystalline and metastable phases is discussed by McCormick in ch. 160. Many times these states of matter are used as intermediates for forming equilibriiun materials ty additional processing steps. These include the rare-earth permanent-magnet materials SmCos, Nd2Fel4B and Sm2Fei7N. Also as described, this technique can be used to refine metals and compounds, and induce other chemical reactions at or near room temperature. 

S, sand cast P, permanent mold cast D, pressure die cast. Aluminum and impurities constitute remainder. Table 22. Mechanical Properties of Aluminum Foundry Alloys ... 

Interstitial mechanism (Figure 8.3A). The displacement of metal atoms takes place from one interstitial site to the other without permanently displacing the matrix atoms in the crystal cell. The distortion caused by the movement of the matrix atoms to allow the jump constitutes the energy barrier that must be surmounted. This mechanism is frequently used to describe him formation on metal alloys when metal atoms normally occupy interstitial positions. 

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