Deformation twinning in the C15 cubic Laves phase of this alloy system was analyzed, at temperatures of between 77K and ambient, by means of conventional and high-resolution transmission electron microscopy. In order to reduce the stacking fault energy, alloy compositions were chosen such that the cubic Laves phase composition was close to a region of C14 phase stability. A high density of stacking defects of intrinsic nature, in the as-homogenized alloy, confirmed that the stacking fault energy was reduced. Twinning was observed at all temperatures, and this placed a low upper limit on any thermally activated deformation process. Twin clusters were observed which were narrow and had a similar distribution to that of the stacking defects in the undeformed alloy. The structure of twins and stacking defects was resolved via high-resolution electron microscopy, combined with image calculations. The use of alloying to control stacking-fault energy, or to refine the microstructure and increase the low-temperature ductility of intermetallic compounds with complex cubic structures, was proposed.

Deformation Twinning at Low Temperatures in a Hf-V-Nb Cubic Laves Phase D.E.Luzzi, G.Rao, T.A.Dobbins, D.P.Pope: Acta Materialia, 1998, 46[8], 2913-27