Hard magnetic SmCo5-Sn nanocomposites produced by high-pressure torsion

High-pressure torsion of powder blends is used as an unconventional process route for the production of textured magnetic SmCo 5 -20 wt% Sn nanocomposites. The use of powders as precursors which get consolidated by the process, enables to overcome limitations of conventional sintering based routes, as the hard magnetic phase and the grain boundary phase can be freely selected. Simultaneously, the microstructure can be adjusted by different process parameters. In this work, Sn is used as binder phase to magnetically decouple the SmCo 5 particles and thus enhance magnetic hardening effects while simultaneously it is not soluble within the SmCo 5 phase, thus preventing or rather delaying mechanical alloying effects. The influence of different number of rotations on the microstructure and the accompanied magnetic properties is investigated. With increasing number of rotations and thus strain, a grain refinement up to the single magnetic domain particle size (∼1 μ m) is observed, which leads to a magnetic hardening up to a coercivity of μ 0 H c = 1.77 T and the formation of a macroscopic texture. With further refinement the coercivity decreases again. This decrease is ascribed to amorphization and intermixing of the two constituent phases SmCo 5 and Sn as observed by transmission electron microscopy and atom probe tomography investigations. The detailed analyses of the interphases and their effect on the magnetic properties can be used to develop optimization strategies for the production of magnetic nanocomposites by high-pressure torsion. • High-pressure torsion applied to powder blends of SmCo 5 -Sn was used to produce hardmagnetic nanocomposites • A coercivity of up to μ 0 H c = 1.77 T was achieved for the nanocomposite subjected to 50 rotations • APT investigations reveal intermixing, resulting in broadening of phase boundaries • At very large strains, partial amorphization and strong intermixing lead to reduced coercivities