Structure and Properties Evolutions for Hard Magnetic MnAl and MnGa Based Alloys Prepared by Melt Spinning or Mechanical Milling

Abstract

Mn-based alloys are generally thought to be the potential rare earth free permanent magnets with acceptable magnetic properties due to its available high magnetization and anisotropy field. In this work, MnAl and MnGa based alloys have been investigated regarding to their processing, structures and magnetic properties. MnAl based alloys with various C additions and/or trace rare earth doping were prepared by melt spinning. The phase transitions during rapid quenching and post annealing were investigated. The composition and annealing process dependent magnetic properties were obtained. The anisotropic MnAlC flakes with improved magnetic properties were also fabricated by surfactant assisted ball milling using alloy ingot as the precursor. The effects of ball milling and post annealing processes on the phase structure and magnetic properties were discussed. As for Mn-Ga alloy, Mn 70Ga30 binary alloy were prepared by melt spinning followed by post heat treatment. The preliminary results show relatively high coercivity. In addition, the prospect of MnAl and MnGa based alloys for permanent magnet applications were discussed in this paper.