Creep mechanisms in niobium-silicide based in-situ composites

This paper will discuss the relationship between microstructure and creep behavior in high-temperature niobium-silicide based in-situ composites. The creep behavior of composites generated from binary Nb-Si alloys, and higher order alloys containing Mo, Hf and Ti additions, will be described. In-situ composites were tested in compression at temperatures up to 1,200 C and stress levels in the range 70 to 280MPa. It was found that the Hf concentration can be increased to 7.5 with little increase in creep rate, over that for the binary Nb3Si-Nb composite, but at higher concentrations the creep rate is increased at stress levels higher than 210MPa. At stresses less than 210MPa the Ti concentration can be increased to 21 without a detrimental effect on creep performance, but at higher concentrations there is a substantial increase in the creep rate