Abstract
With the object of elucidating the cause of Perminvar characteristics of the “Senperm” alloys containing 14∼18%Ni, 8∼12%Si and the remainder Fe, which was discovered by T. Yamamoto about ten years ago, the constitutions of alloys containing 15 at%Ni and 5∼25 at%Si were investigated by means of microscopic observation magnetic and dilatometric analyses as well as measurements of electric resistance and intensity of magnetization, through which the sectional diagram of 15 at%Ni was determined. There exists no superlattice as inferred by T. Yamamoto, but a ferromagnetic ternary compound named the σ-phase by the authors precipitating from the α-phase is formed. Measuring the B-H curves of several alloys under various heat-treatments with ballistic galvanometer method, it was also found that the striking Perminvar characteristics was obtained when the σ-phase was precipitated in dispersed state, through furnace cooling from about 900°. Considering these results, the Perminvar characteristics of the “Senperm” alloys was attributed to some dispersed precipitation of the σ-phase in the matrix of the α-phase.
