Properties in Reactive Structure Materials: ZrW 2 and HfW 2 – High Melting Temperatures, Densities, Hardness, and Exothermic Ignition Energies

ZrW 2 and HfW 2 were prepared by melting the constituent elements in an arc‐furnace. By cooling through perictectic phase lines above approximately 2000 °C, samples of the nominal 1:2 composition were obtained as products consisting of two phases, of which approximately 95 % adopts the MgCu 2 type structure and 5 % the W structure. In ZrW 2 and in HfW 2 , the MgCu 2 type structure enables efficient topological compact spacefilling of the smaller W atoms into the cavities of the three‐dimensional net constructed by the larger tetravalent metals Zr and Hf. Correspondingly, very dense and hard alloys are obtained which burn at a crash in air in a strong exothermic ignition reaction. These materials are non‐toxic.