Design of (Hf, Ta)Fe2/Fe composite with zero thermal expansion covering room temperature. (September 2020) - Cen, Dongyu
Abstract: MgZn2 -type (Hf, Ta)Fe2 is a typical negative-thermal-expansion system, which expands during the establishment of ferromagnetic ordering in cooling. This abnormal behavior suggests that (Hf, Ta)Fe2 is a potential ingredient to produce a composite with zero thermal expansion. In this work, we find that the as-cast (Hf, Ta)Fe2 have Fe-rich grain boundaries, which disappear after annealing. It inspires us to produce a (Hf, Ta)Fe2 /Fe composite by adding extra Fe in nonstoichiometric composition without annealing. After carefully tuning Hf/Ta ratio and Fe concentration, room-temperature zero-thermal-expansion is achieved in the sample with a composition of Hf0.80 Ta0.20 Fe2.5 . Graphical abstract: Image, graphical abstract