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.