The Effect of Silicide Volume Fraction on the Creep Behavior of Nb-Silicide Based In-Situ Composites


This paper will describe the creep behavior of high-temperature Nb-silicide in-situ composites based on quaternary Nb-Hf-Ti-Si alloys. The effect of volume fraction of silicide on creep behavior, and the effects of Hf and Ti additions, will be described. The composites were tested in compression at temperatures up to 1200oC and stress levels in the range 70 to 280 MPa. At high (Nb) phase volume fractions the creep behavior is controlled by deformation of the (Nb) and, as the volume fraction of silicide is increased, the creep rate is reduced. However, at large silicide volume fractions (>0.7) damage in the silicide begins to degrade the creep performance. The creep rate has a minimum at a volume fraction of ~0.6 silicide. The creep performance of the monolithic and silicide phases will also be discussed.

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The authors would like to thank D.J. Dalpe for the directional solidification, and C. Bull for assistance with creep testing. This research was partially sponsored by AFOSR under contract #F49620-00-C-0014 with Dr. C.S. Hartley and Dr. S. Wu as Program Managers.

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Correspondence to B.P. Bewlay.

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Bewlay, B., Briant, C., Davis, A. et al. The Effect of Silicide Volume Fraction on the Creep Behavior of Nb-Silicide Based In-Situ Composites. MRS Online Proceedings Library 646, 167–172 (2000).

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