MnAlの磁性に対する粉砕およびスエージングの影響

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  • On the Effect of Pulverizing and Swaging on the Magnetic Properties of MnAl Compound
  • MnAl ノ ジセイ ニ タイスル フンサイ オヨビ スエージング ノ エイキョウ

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With the object of improving the properties of MnAl compound suitable for the application to permanent magnet, the effect of pulverizing and swaging on the magnetic properties of MnAl, especially on its coercive force, has been studied.<BR>When MnAl is pulverized in a ball mill, IHC increases at the expense of Br. Pulverizing in a hammer mill produces a striking increase in IHC and after being pulverized 130 times in the mill, IHC reaches the highest value of 6500 Oe. The relation between IHC and grain size of the hammer milled MnAl powder shows close resemblance to those of Ba ferrite, MnBi and Fe3O4, but an increase in IHC takes place at far more coarse grains than in the case of these typical single domain magnets. Saturation magnetization Is, lowerd by hammer milling is recovered by tempering, and the increased IHC is reduced. The permanent magnet properties obtained are not sufficent to practical applications. Magnetic press was not recognized to be effective.<BR>MnAl bars swaged at room temperature by the reduction of 86% and 71% improved IHC to be 4000 Oe and 3000 Oe respectively. Decrease in saturation magnetization by swaging was not observed. Saturation magnetization and maximum energy product of the swaged MnAl is raised by tempering. Swaging at 400°C gives the result inferior to room temperature swaging.<BR>MnAl containing Ti, especially, the specimen having a high Is×IHC value (68.93%Mn, 28.16%Al, 1.94%Ti and 0.97%Cu) shows a remarkable increase in IHC and decrease in Is by swaging at room temperature. When tempered, this specimen acquires excellent permanent magnet properties. For example, the specimen swaged by 84% and tempered at 500°C for 1 hr has the following properties; Br=4840 gauss, IHC=3100 Oe, BHC=2400 Oe and (BH)max=4.5×106 gauss·Oe. This (BH)max value is higher than that obtained by Koch et al. with MnAl containing no additional element.<BR>On the MnAl specimens containing Ti, swaged and tempered, the magnetic anisotropy energy derived from approach to saturation seems to be proportional to Is×IHC. This fact may give a suggestion on the mechanism of coercive force of swaged MnAl.

収録刊行物

  • 日本金属学会誌

    日本金属学会誌 28 (8), 483-489, 1964

    公益社団法人 日本金属学会

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