Landolt-Börnstein - Group III Condensed Matter Fe-24 wt % Co-Ni-Al-Cu alloy system


This chapter deals with phase diagrams and magnetic properties of Fe-24% Co-Ni-Al-Cu alloy system. Vertical sections of phase diagrams for alloy compositions close to Fe-24Co-14Ni-8Al-3Cu (Alnico 5) are given. The phase constitution changes from a single α phase at high temperature into two phases. α1 and α2 at lower temperatures, inevitably passing through the (α + γ) two-phase region in the intermediate temperature range. The temperature-time transformation (TTT) curves shown here indicate that a rapid cooling or quenching of the alloy can result in a single α phase at ≈ 900°C. A typical preparation process of this magnet alloy including low-temperature homogenization, controlled magnetic cooling and quenching followed by subsequent double aging is shown. Further, the variation of the dimensions of the ferromagnetic particles during the thermomagnetic treatment and the subsequent aging process of the alloy is given. A reproduced Mossbauer spectrum of the alloy is shown. It is illustrated that the permanent magnetic properties are represented for noncolumnar samples with alloy compositions around Fe-24Co-14Ni-8Al-3Cu which were subjected to an optimal processing procedure. It is evident that in this system the standard composition alloy is most favorable as a magnet alloy. The influence of temperature on these properties is also shown. The relation between the magnetic properties and the preparation technique is given. For columnar alloys and 'single crystal'-type samples obtained from these alloys the magnetic properties are given in relation to the applied preparation technique.

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Title Fe-24 wt % Co-Ni-Al-Cu alloy system
Book Title
Magnetic Alloys for Technical Applications. Hard Magnetic Alloys
In Fe-Ni-Al base magnet alloys
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Chapter DOI
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Landolt-Börnstein - Group III Condensed Matter
  • H. P. J. Wijn
  • Authors
  • T. Nakamichi
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