Influence of annealing on the microstructure and magnetic properties of the τ-MnAl alloy deformed by high pressure torsion

•The best coercive force (3.7 kOe) in this study was reached after HPT deformation by 20 revolutions.•Twinned structure obtained by severe plastic deformation is preferable for recrystallization.•Recrystallized grains have an average size of ≈ 1.7 µm that results in low coercive force. Ferromagnetic alloys of the Mn-Al system are promising materials for permanent magnets and details of electric motors. Deformation methods of processing these alloys allow obtaining high magnetic properties, however, they are still not well researched. In the current study the effect of the τ-MnAl alloy structure obtained by severe plastic deformation on the phase composition, structure, and magnetic properties gained during subsequent annealing is investigated. It was shown that a twinned structure is preferable for recrystallization (in terms of recrystallized volume) than a dislocation one. The largest coercive force of 3.7 kOe was reached in the current investigation after deformation by 20 revolutions (ε ≈ 6.83). Subsequent annealing led to a drastic fall in coercive force due to vanishing of defects (dislocations and nanotwins) acting as sites of domain wall pinning.