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Abstract
Grain boundary faceting and annealing twins in a Hf—V—Nb-based C15 intermetallic compound were studied using transmission electron microscopy. Approximately 5% of the boundaries become faceted during annealing at 1200°C and the majority of completely faceted boundaries are [Sgrave]3(〈110〉/70·53°) grain boundaries. About 65% of the facets were found to be of the type {111}1/{111}2, with the balance being {112}1/{112}2, {111}1/{115}2 and {001}1/{221}2. A facet in the process of transformation was also observed: [Sgrave]3{111}1/{115}2 → [Sgrave]3{111}1/{111}2 + [Sgrave]3{112}1/{112}2. Annealing twins in the bulk were identified as {111}〈112〉 type and a mechanism for the growth of annealing twins based on the faceting reaction is proposed. In this mechanism annealing twins grow by the anisotropic migration of [Sgrave]3{112}1/{112}2 facets via the slip of synchro-Shockley partial dislocation triplets.
