Soft magnetic alloys customized for spring magnets

ENG- Spring magnets have gained popularity as an economical and sustainable alternative to rare-earth permanent magnets. A spring magnet is a composite material that achieves magnetic exchange coupling between soft and hard magnetic particles. Therefore, optimizing these magnetic particles is vital to the successful manufacture of a spring magnet. This thesis is focused on optimizing two Fe-based soft magnetic alloys, obtained by mechanical alloying, that could act like a magnetic reinforcement for a hard magnetic alloy to obtain a spring magnet. The optimization of these alloys is achieved by favouring their nanocrystallinity and reducing the average particle size. The results clearly show a successful optimization for longer milling times and an even further optimization with the addition of a process control agent (PCA) during milling. The addition of a PCA also favours the formation of additional metastable tetragonal phases. These tetragonal phases, which are magnetically harder, alter the direct correlation between the soft magnetic response of the alloy with their optimization. However, a successful correlation between the optimization of the alloys and their magnetic response is obtained. The final part of the study focuses on composites. The first composite corresponds to a first attempt at a spring magnet between one of the Fe-based soft magnetic alloys of the thesis and a commercial iron oxide acting as the harder magnetic phase. Full exchange coupling between particles is not achieved. The second composite is an additive manufactured polymer-metallic material. The results show how a structurally functional polymer-metallic composite can be manufactured and could be an alternative to the more traditional sintering techniques that require high temperature and pressure