Elimination of the non-recrystallised regions in the extruded MnAl-C-Ni magnet using pulverised melt-spun ribbons

Abstract

MnAl-C-Ni magnets with maximum energy products, (BH)max ≥ 42 kJ m−3, were produced by hot extruding pulverised melt-spun ribbons. The small diameter of the columnar grains in the as-spun ribbons (1 µm ≤ d ≤ 6 µm), restricted the maximum size of the τ-phase grains, which formed during the holding process at 700 °C before the extrusion. The absence of non-recrystallised regions in the extruded material made from ribbons produced at high wheel speed was attributed to this smaller initial τ-phase grain size (1 µm ≤ d ≤ 2 µm) and resulted in an enhancement of the squareness factor of the demagnetisation curve.