Effect of Grain-Boundary Phase
نویسندگان
چکیده
Two types of hot-pressed silicon nitride, one having an amorphous grain-boundary phase (6 wt% yttria, 3 wt% alumina) and the other having a predominantly crystalline grain-boundary phase (8 wt% yttria, 1 wt% alumina), were tested on a split Hopkinson pressure bar with a momentum trap, such that, in each test, the sample was subjected to a single predefined stress pulse and then recovered without being subjected to any other loads. The specimens were loaded repeatedly with a triangular pulse of 3.2 GPa amplitude at a strain rate of approximately 400/s. The dynamic fatigue life of amorphous grain-boundary-phase silicon nitride was observed to be higher than that of the corresponding fatigue life of crystalline grain-boundaryphase silicon nitride. The difference in fatigue lives is correlated to the microstructural damage occurring in both materials.
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