Room temperature deformation behavior of the Hf–V–Ta C15 Laves phase

We report the extensive room temperature ductility in Laves phase/bcc two-phase alloys in the ternary HfV2+Ta alloy system. First, the ternary phase diagram of the Hf–V–Ta alloy system at 1373 K is investigated by metallography, X-ray diffraction and scanning electron microscopy equipped with wave length-dispersive X-ray fluorescence spectroscopy. The Laves phase formed in the Hf–V–Ta ternary alloys has widened off-stoichiometric range in the middle of HfV2–TaV2 pseudo-binary line, and is composed of the C15 Laves phase. A bcc solid solution is formed on the vanadium-rich side with small solubilities of less than 10 at.% for Hf and Ta. Test samples were produced with equilibrated microstructures consisting of C15 Hf2V+Ta and the bcc V solid solution. Compression tests are carried out at room temperature in order to understand the effects of bcc volume fraction and Ta alloying on the mechanical properties of the alloys. Ductility is found even in alloys with a Laves phase matrix. Transmission electron microscopic observation indicates that {111}<112> twinning is responsible for the room temperature ductility.