Hard magnetic properties

Vanadium—Cobalt-Iron Alloys. V—Co—Fe permanent-magnet alloys also are ductile. A common commercial ahoy, Vicahoy I, has a nominal composition 10 wt % V, 52 wt % Co, and 38 wt % Fe (Table 10). Hard magnetic properties are developed by quenching from 1200°C for conversion to bcc a-phase foUowed by aging at 600°C (precipitation of fee y-phase). The resulting properties are isotropic, with ca kJ/m ... 

Texture has a rather marked influence on the properties of a given deposit. Thus, rather seemingly umelated parameters (properties), such as corrosion resistance, hardness, magnetic properties, porosity, contact resistance, and many others, are all texture dependent. By way of illustration, we discuss (6) first the case of magnetic properties. 

The magnetic properties of these compounds and hence their applications are closely coupled to their crystal structure. This is the basis of their classification into ferrites with soft magnetic properties (cubic) and hard magnetic properties (hexagonal). 

The slightly reduced values of the room-temperature anisotropy fields when relatively small amounts of Fe in R2Fe14B are replaced by Co (see fig. 19) are not the only reason why Co substitution does not lead to improved hard magnetic properties. This is true for the temperature coefficient of the coercive force in particular. A probable reason for this is that not only JIA itself but also its temperature dependence becomes less favourable upon Co substitution. This may be inferred already from a comparison of the temperature dependences of HA in the pure ternaries Nd2Fe14B and Nd2Co17B shown in fig. 21, where it can be seen that the slope of the HA(T) curve for the latter compound around room temperature is much steeper than that of the former. In fact, the HA(T) curve in Nd2Co14B tends to approach the horizontal axis at a temperature of about 540 K, which is still far below the corresponding Curie temperature (Tc = 1007 K). The most obvious... 

The substitution of C for B in R2Fe14B presents considerable metallurgical difficulties. Extensive studies of the possibility of this type of substitution were made by Liu et al. (1987) and results of their investigations have already been reproduced in fig. 6. The effect of C substitution is to increase the hard magnetic properties (Liu and Stadelmaier 1986, Bolzoni et al. 1985). The latter authors reported that the room-temperature anisotropy field in Nd2Fe14B1 xCx increases... 

Fig. 35. Comparision of the hard magnetic properties of two hard magnetic materials a and b. (Left) Flux density B (full lines) and magnetic polarization J (dashed lines) as a function of the demagnetizing field strength H. (Right) Product BH (horizontal axis) plotted versus B (vertical axis) for both materials a and b. The working point corresponding to (BFf)max is indicated on the B(H) curve (left point for material a and b) by a filled and open circle, respectively.

At the end of the 1960s, a new material with exceptional hard magnetic properties (Table 6.7) was prepared samarium-cobalt, SmCoj. Its most outstanding property is its magnetocrystalline anisotropy reported values are in the range (11-20) x 10 J/m (by comparison, Ba ferrite has an anisotropy of 0.33 x 10 J/m, Table 4.15). Rather than being a serendipitous discovery, the successful synthesis of SmCoj was the result of a systematic effort (Strnat, 1988). 

Kas] DTA, microstmcture analysis, hardness, magnetic properties, thermal expansion measurements Liquidus surface, vertical sections below solidus at 10, 20, 30, 40, 50, 60, 70, 80, 90 mass% Ni and 10, 20, 30, 60, 80 mass% Co / full concentration interval. 

Inoue, A. Takeuchi, A. Makino, A. Masumoto, T. (1995b). Hard magnetic-properties of nanocrystalline Fe-iich Fe-Nd-B alloys prepared by partial crystallization of amorphous phase. Materials Transactions JIM, Vol. 36, No. 7, (July 1995), pp. 962-971, ISSN 0916-1821... 

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