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The effect of Ru on microstructure and stress rupture properties of an advanced Ni base single crystal alloy has been investigated. The experimental results showed that the addition of 4 wt.% Ru had hardly effect on the phase precipitation behavior of as-cast alloy, i. e., the microstructure is composed of γ and γ' phases for both Ru free and Ru containing alloys. However, under the heat treatments of 1305℃-1315 /16h ℃ solutioning and 1140℃/4h＋ 870 /20h ℃ aging, and the thermal exposure under 1100 /1000h, ℃ the addition of 4 wt.% Ru restrained the precipitation and growth of TCP phase evidently, and increased the rafting structure tendency of γ/γ' phases. The results of stress rupture tests showed that the addition of 4 wt.% Ru in the alloy improved the stress rupture lives significantly for as-cast, as-heat treated and thermal exposed samples. The improvement of the stress rupture properties may be attributed to the restraint of μ phase precipitation and growth by the proper addition of Ru.

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