Abstract
It is theoretically and experimentally shown that Ge has an excellent refining effect on the vacuum melting of Fe-Ni alloys. Therefore, it is presumed that the grains of Fe-Ni alloys containing a few %Ge are generally easy to grow and the alloys have superior magnetic properties, because of the decrease in the gas content and non-metallic inclusions. From the above standpoint, the author has studied how the grains and the magnetic properties of Fe-Ni alloys containing Ge change during the recrystallization treatment. The results obtained are as follows:
(1) The addition of Ge promotes remarkably the grain growth, which is particularly effective by the initial addition of only a few %Ge. The reason is that the non-metallic inclusions are removed out by the refining action of Ge.
(2) The addition of Ge induces a substantial decrease in the coercive force, resulting in improvement of the magnetic properties. The effect is also remarkable by the addition of only a few %Ge.
(3) The activation energy for the grain growth is calculated to be about 20000 cal/mol in all of Fe-Ni alloys. This value is relatively small and is close to that of the diffusion of atoms along the grain boundaries. On the other hand, the frqeuency factor in Fe-Ni alloys containing Ge is the largest, the easy grain growth of which is due to their large frequency factor value.
