Influence of carbides on the strength and toughness of a niobium alloy

The mechanical behaviour of Nb35Ti6Al5Cr8V (at.-%) containing different C contents (0, 1 and 10 at.-%) has been investigated. The addition of 1 at.-%C does not increase the strength at room or high temperature, whereas adding 10 at.-%C improves significantly the strength at both room and high temperature. Adding 1 at.-%C slightly increases the fracture toughness; aging the same alloy for 9 days also results in a slight improvement in the toughness. A 10 at.-%C addition, however, leads to a dramatic decrease in the toughness. The variation in the toughness is linearly related to the proportion of cleavage as modified by the carbide.