Large Scale PM Process for Producing Magnetocaloric Heat Exchanger

摘要

In this paper, we present a powder metallurgy process based on gas atomization to produce qualityLa(Fe,Si)_(13) based hydrogenated magnetocaloric materials. With this process, shaped pieces ready-touseinto refrigeration devices can be produced. The rapid solidification occurring during the first gasatomization step prevents the La-Fe-Si-type alloy from forming very large α-Fe dendrites duringcooling, allowing to easily and efficiently heat treat the obtained powder to form the magnetocaloricNaZn_(13)-type intermetallic. In this process, a batch of several hundreds of kg of alloy is first gasatomized into powder. The powder is then annealed at 1373 K under Ar for one hour to reach around95% of magnetocaloric phase, and subsequently hydrogenated. Finally, the powder is shaped intocomposite products containing 91.5 wt.% of powder, by extrusion. This process induces no loss ofmaterial and allows producing non fragile pieces comprising thin sections.