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The effects of restoration and certain elements, nitrogen, sulphur, calcium and Misch metal, on the hot ductility of austenitic, high-alloyed austenitic and duplex stainless steels have been investigated by means of hot rolling, hot tensile, hot bending and stress relaxation tests. The results of these different testing methods indicated that hot rolling experiments using stepped specimens is the most effective way to investigate the relationship between the softening and cracking phenomena under hot rolling conditions. For as-cast, high-alloyed and duplex stainless steels with a low impurity level, the cracking tendency was observed to increase with increasing pass strain and temperature, being minimal for the small strain of 0.1. No cracking occurred in these steels when rolled in the wrought condition. It could be concluded that the cracking problems are only exhibited by the cast structure with the hot ductility of even partially recrystallised steel being perfectly adequate. However, the recrystallisation kinetics of the high-alloyed austenitic stainless steels, determined by stress relaxation and double-pass rolling tests, were found to be so slow that only partial softening can be expected to occur between roughing passes under normal rolling conditions. In the duplex steel, the restoration is fairly fast so that complete softening can occur within typical interpass times in hot rolling, while certain changes in the phase structure take place as well. Sulphur was found to be an extremely harmful element in duplex stainless steel with regard to their hot ductility so that severe cracking can take place with sulphur content above 30 ppm. However, the effect of sulphur can be eliminated by reducing its content and by calcium or Misch metal treatments that significantly increase the number and decrease the average size of the inclusions. It seems that the desulphurisation capacity of an element is the most important property for assessing its usefulness in reducing the detrimental influence of sulphur. The hot ductility of type 316L stainless steel determined by tensile tests was found to be better for nitrogen content of 0.05 wt-% than 0.02%, while in double-hit tensile tests the hot ductility values were identical. The mechanism whereby nitrogen affects hot ductility remains unclear but a retarding effect on static recrystallisation was observed.

The easy- and hard-axis magnetization behaviour has been studied in detail in a Mm 2 Co 16.5 Zr 0.5 pseudomonocrystal, where Mm is cerium misch-metal, in the temperature range 4.2–290 K. At room temperature, the magnetocrystalline anisotropy of the compounds is uniaxial with the easy direction along the c -axis of the hexagonal cell. However, when the temperature decreases the anisotropy becomes cone-like, with the easy directions forming at 8 K a cone with an angle of 70° with respect to the c -axis. This transition is explained in terms of the competition between the anisotropies of the Co and R sublattices.

The magnetic behaviour in Dy1-xMmxCo2 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; Mm = mischmetal) compounds is reported using temperature and field dependence of magnetization (M-T and M-H respectively) measurements. A strong composition dependent irreversibility is observed in both the M-T and M-H scans below the magnetic ordering temperature (TC). A clear change of the first-order magnetic transition of DyCo2 to a second-order one in Dy0.5Mm0.5Co2 is evidenced by M-T and a series of Arrott (M2 versus H/M) plots, obtained from the M-H isotherms around TC. The variation in induced moments of the Co sublattice is estimated. It is found that the Mm substitution can only lead to a considerable reduction in the TC, saturation magnetization, and Co moment. The observed behaviour of M-T and M-H plots with increasing Mm content is discussed in detail. � 2010 IOP Publishing Ltd.

Total RE, Co and Fe in mischmetal and its cobalt alloys are determined by visual complexometric methods and instrumental x-ray fluorescence techniques. As Fe causes interference in the determinations of RE and Co and its own determination is affected by the presence of Co, it is removed by precipitation. The iron is determined from the precipitate and RE and Co from the filtrate. Accuracy of the method is checked by analysing synthetic mixtures of RE, Co and Fe. The individual REs in mischmetal are determined by x-ray fluorescence method. The analysis technique is based on comparison of the oxides of the test samples with standards (both in pressed pellet form) in the appropriate composition range. The total RE content of mischmetal determined through complexometric analysis is compared with the total RE determined through x-ray fluorescence.

In order to reduce the large hysteresis effect in MmNi hydrides (Mm  misch metal) we studied the hydrogen absorption-desorption characteristics of multicomponent alloys such as MmNi5−xAl(Mn)y−zMz and MmNi5−xAl(Mn)yM2 (M = Co, Cr, Cu, Nb, Ti, V, Zr; x = 0.3 − 0.5; y = 0.3 − 0.5; z = 0.05 − 0.1). The substitution or addition of the element M eliminates the large hysteresis effect that occurs during an absorption-desorption cycle. The hysteresis factor (equal to In( P a P d )) for MmNi4.7Al0.3M0.1 hydrides decreased for additives M in the following order: Zr > Co > Cr > Ti,V > Cu. Investigations of the effects of cycling showed that spalling occurred more rapidly for MmNi4.5Mn0.5 than for MmNi4.5Mn0.5Zr0.005 and MmNi4.5Mn0.5Zr0.1.

Electrical resistivity measurements of LaNi 5 and MmNi 4.5 Mn 0.5 (Mm  misch metal) films which were obtained by vacuum vapour deposition were carried out in an atmosphere of hydrogen. Resistivities of the films initially increased immediately and then decreased during the absorption process of hydrogen. The reverse is true for the desorption process. The intermetallic compound films did not pulverize even after 150 cycles of absorption-desorption of hydrogen if the thickness of the film was less than 10 × 10 4 nm.

The design and performance of a 1 kg MmMg 12 hydride tank (Mm ≡ misch metal) is described. It operates at temperatures of 250–400 °C using electrical heaters. Provisions were made to operate it using hot gas. The desorption rate is a function of the heat supply and at 200 W it can supply 12 1 min −1 . Cycling measurements performed on a smaller tank with a similar design containing 0.17 kg MmMg 12 showed that the absorption rate and the total capacity were not affected by cycling up to 70 cycles. However, the desorption rate decreased by 50%. We suggest that the discrepancy between the deterioration of the desorption rate compared with almost no effect on the absorption rate and capacity as a function of cycling is due to the decrease in the heat conductivity of the hydride. Such a decrease is expected as the grain size of the MmMg 12 decreases with cycling.

Rare earths, primarily light rare earths, either alone or in combination with other rare earths, as in misch metal, alloyed with cobalt or iron, constitute a unique new class of permanent magnet materials with outstanding coercivity and other magnetic properties. These materials represent the first serious alternative to the alnicos and ferrites, discovered earlier. The intensity of interest in this field may be judged by the presence of over 800 publications which have appeared in the 25 years since their discovery and by the fact that the publication rate remains unabated. The present bibliography includes a listing of references by year and indexes based on subject, material and author.

AB5型の六方晶構造をもつ, RNi4.8Al0.2 (R : 希土類成分) 合金の水素化, および水素化物の脱水素化反応速度を測定し, その解析を行った.解析では, 反応速度に影響を及ぼす各種要因を定量的に検討し, 水素化物の平衡圧力と雰囲気中の水素圧力との圧力差が, 水素化物濃度に比較して, 大きな推進力となることを明らかにした.希土類成分Rに関しては, La, NdおよびPrの含有量の多い混合物の方が水素化, 脱水素化ともに反応速度が速いことを見いだした.また, MmNi4.5Al0.5-水素化物の文献データとの比較により, Niの一部をAlで置換することで, 反応速度が迅速になることが確かめられた.La単体および希土類成分の混合物からなるRNi4.8Al0.2-水素化物を定圧系で水素吸蔵反応を起こさせた場合, 反応速度定数と反応の推進力である平衡圧力と操作圧力との圧力差を掛けたN-値は, 従来の反応速度定数K-値と異なる挙動を示し, 最大値を示す温度領域が存在することがわかった.