Effect of C Addition on the Microstructure and Fracture Properties of In Situ Laminated Nb/Nb5Si3 Composites

//Nb-ss and alpha-Nb5Si3 phases were detected. Meanwhile, Nb2C was observed, and the crystal forms of Nb5Si3 changed in the C-doped composites. Furthermore, micron-sized and nanosized Nb2C particles were found in the Nbss layer. The orientation relationship of Nb2C phase and the surrounding Nb-ss was [001](Nbss)//[010](Nb2C), (200) (Nbss)//(101) (Nb2C.) Additionally, with the addition of C, the compressive strength of the composites, at 1400 degrees C, and the fracture toughness increased from 310 MPa and 11.9 MPa .m(1/2) to 330 MPa and 14.2 MPa .m(1/2), respectively; the addition of C mainly resulted in solid solution strengthening.