Production of net-shape Mn-Al permanent magnets by electron beam melting

The main goal of this work is the adoption of additive manufacturing for the production of inexpensive rare-earth free MnAl-based permanent magnets. The use of more advanced binder-free additive manufacturing technique such as Electron Beam Melting (EBM) allows obtaining fully-dense magnetic materials with advanced topology and complex shapes. We focus on the feasibility of controlling the phase formation in additively manufactured Mn-Al alloys by employing post-manufacturing heat treatment. The as-manufactured EBM samples contain 8% of the desired ferromagnetic τ-MnAl phase. After the optimized annealing treatment, the content of the τ-phase was increased to 90%. This sample has a coercivity value of 0.15 T, which is also the maximum achieved in conventionally produced binary MnAl magnets. Moreover, the EBM samples are fully dense and have the same density as the samples produced by conventional melting density.