Effect of carbon on the microstructures and mechanical properties of as cast Nb-base alloy

Microstructure and mechanical properties of Nb35Ti6Al5Cr8V (at.%) containing different C contents (0, 1, 11.6 at.%) were investigated. The microstructures were characterized using optical microscopy and scanning and transmission electron microscopy (SEM and TEM, respectively). The alloy without C appeared single phase: Nb solid solution (Nbss). The carbide in 1% C alloy is fcc MC. The addition of 11.6% C resulted in the formation of two types of particles: primary carbide ((Ti,Nb)2C) and secondary carbide ((Ti,Nb)C). Compression testing was carried out at room temperature, 1073, 1273 and 1473 K. The alloys showed good compression ductility at room temperature. The strengths at room and high temperature increase with increasing C content, but the room temperature ductility decreases.