Superplasticity of multiphase refractory Nb-16Si-2Fe in situ composite

A multiphase refractory Nb-16Si-2Fe in situ composite was prepared by mechanical alloying (MA) and hot pressing sintering. Analysis of XRD reveals that the composite consists of Nb solid solution (Nbss), intermetallics Nb₃Si, Nb₅Si₃ and Nb₄Fe₃Si₅. The average grain sizes of each phase are all about 3 μm and the grains shapes are nearly equiaxed. This composite exhibits excellent superplasticity due to a big amount of liquid phase Nb₄Fe₃Si₅ at the temperature 91°C higher than the solidus temperature of 1359°C. The tensile elongation of 512% is obtained at 1450°C. Microstructures of the deformed specimen and analysis of DSC experiment indicate that the main mechanism for superplastic deformation of this composite is viscose flow of the liquid phase Nb₄Fe₃Si₅, which is obviously different from that of conventional magnesium-based and aluminum-based composites accommodated by liquid phase.