Eutectoid decomposition of βNb₅Si₃ → αNb₅Si₃ + Nbss in Nbss/Nb₅Si₃ in-situ composites revealed by electron microscopy

Eutectoid decomposition of βNb₅Si₃ → αNb₅Si₃ + Nbss in Nbss/Nb₅Si₃ in-situ composites has been systematically investigated by electron microscopy. βNb₅Si₃ would transform into different αNb₅Si₃ orientation variants around 1075 °C. There is no inherent orientation relationship (OR) between βNb₅Si₃ and αNb₅Si₃, which might be regulated by the diffusive nature of the transformation. Numerous Nbss precipitates would form within αNb₅Si₃ with crystallographic OR of <001>_Nb// < 001>_α. This transformation is promoted by formation of dislocations and the diffusion of Nb at elevated temperatures, which will propagate from Nbss/βNb₅Si₃ interfaces to the interior of βNb₅Si₃ grains.