Soft Magnetic Properties of Fe-Ni-Nb Alloy Films
The relation between the soft magnetic properties and local anisotropy fluctuation measured by the dynamic differential susceptibility method in Fe-Ni-Nb alloy films was clarified and discussed in comparison with Fe-Si-Al alloy films. Fe-Ni-Nb alloy films with excellent soft magnetic properties, 5 MHz values of ¿eff = 6500 for 1000 Å thick films were obtained. For Fe-Si-Al alloy films, the magnitude of ¿eff = 6500 is proportional to 1/S2 (where S is a structure constant) and independent of the value of Hk, while for Fe-Ni-Nb alloy films, the value of S is about one-tenth of that in Fe-Si-Al alloy films, and the magnitude of ¿eff 6500 does not depend on S. Rather, this magnitude is dependent on the value of Hk, and is almost equal to 4¿Ms/Hk, obtained from a rotational magnetization model in a uniaxial single-domain particle.
Ni-F-Nb (50Ni-Fe組成) 合金薄膜の軟磁気特性
The relation between soft magnetic properties and local anisotropy fluctuation, which is strongly connected with the microstructure of the films, was systematically examined for Ni-Fe-Nb alloy films with nearly 50 wt%Ni. According to the micromagnetic ripple theory by Hoffmann, effective magnetic anisotropy Ueff in each of the grains decreases drastically with increases in the number of grains N within the coupling volume. Experimental results show local anisotropy fluctuation for Ni-Fe-Nb alloy films strongly depends on Ueff/Ku, and it decreases with decreasing Ueff/Ku. Therefore, to realize high initial permeability in these films, it is necessary to increase N within the coupling volume by decreasing the size of the grains. In the case of Ni-Fe-Nb alloy films, decreasing the size of the grains less than 200A to obtain high initial permeability more than 2000 is needed.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.