Makoto Sugihara

On the Effect of Heat Treatment in a Magnetic Field on Magnetic Properties of Iron-Aluminium Alloys

When the specimens of iron-aluminium alloys were cooled in a magnetic field from high temperatures, the percent increase of initial permeability is generally not large, but that of maximum permeability is considerably large and it has a maximum at the concentration of 10.20 percent aluminium. The effect of heat treatment in a magnetic field is small for the concentration of more than 11.5 percent aluminium. When the quenched specimen of 10.20 percent aluminium was annealed again at various temperatures in a magnetic field and cooled in the field, the lowest effective temperature of heat treatment in a field becomes about 225∼250°C. This temperature is 100°C lower than the usual lowest effective temperature for the specimen without quenching. Maximum permeability of the specimen which was quenched at first and heat treated at about 250°C in a magnetic field reaches to the highest value of about 30,000.

Structural and Magnetic Properties of Copper‐Substituted Manganese‐Aluminum Alloys

Magnetic properties of ternary Cu(0–12.5 at. %) — Mn(55–42.5 at. %) — Al(45%) alloys have been studied in relation to the change of the tetragonal structure from the binary Mn–Al alloy to the ternary alloys. The substitution of Mn by Cu stabilizes the ferromagnetic tetragonal phase of the Mn–Al alloys. An increase of the Cu content brings about a decrease of the Curie temperature, the intrinsic coercive force, and the ratio of remanence to saturation induction. Correspondingly, the introduction of Cu into Mn–Al alloys first reduces the axial ratio c/a of the tetragonal phase from 1.30 in the 55 at. % Mn–Al alloy to 1.20 at 10 at. % Cu, and then converts the tetragonal structure into body‐centered cubic at more than 10 at. % Cu. In the latter case, the ternary alloys are ferromagnetic disregarding aging conditions.

Structural and Magnetic Properties of Copper-Substituted Manganese-Aluminum Alloy

Magnetic and structural properties of the tetragonal phase of ternary Cu (0–12.5 at%)–Mn(55–42.5 at%)–Al(45 at%) alloy have been studied in relation to binary 45Al-Mn alloy. The substitution of Cu to Mn-Al alloy reduces the tetragonality c/a of the tetragonal phase from 1.30 of the 45Al-Mn to 1.20 of the 10 at% Cu alloy, and then changes the structure to cubic at more than 10 at% Cu. An increase of Cu content also results in a decrease of the Curie temperature, of the coercive force and of the ratio of remanence to saturation magnetization.

On the Magnetic Properties of 12 Percent Aluminum-Iron Alloy

A sharp maximum of permeabilities has been found in the narrow concentration range of about 12 percent aluminum in the slow cooled iron-aluminum alloys. It is found, however, that the permeabilities of this alloy are decreased and its coercive force is increased the reheat-treatment at temperatures between 400° and 650°C, followed slow cooling. For example, after reheating the alloy to 550°C µ m was decreased from 23,500 to 4,800, µ 0 from 1,600 to 1,000 and H c was increased from 0.09 to 0.37 Oe. Since such a reheating effect was not found in the other concentration of iron-aluminum alloys, it is concluded that the phenomenon is due to something characteristic of 12 percent aluminum-iron alloy, that is the growth of a small quantity of precipitation or the short range order, which would result in an increase of internal strain.