一种单晶高温合金高温原位拉伸过程中化学腐蚀表面的相转变

Phase Transformation on Chemically Corroded Surface of a Single-Crystal Superalloy During In-Situ Tension at Elevated Temperatures

摘要:

对化学腐蚀后的单晶高温合金进行了980和1100 ℃下的原位拉伸试验。使用场发射扫描电子显微镜、能量色散X射线光谱、电子探针X射线显微分析和透射电子显微镜分析了拉伸过程中表面的相变过程。通过观察和动力学计算相结合，研究了合金表面相变机理及其对合金的影响机理。结果表明：在高温拉伸过程中，化学腐蚀促进了合金表面μ相和σ相等拓扑密排（tcp）相的析出。在1100 ℃下，2种相在表面的析出量和尺寸均大于980 ℃下的析出量和尺寸。tcp相在合金表面的析出导致了表面区域1层影响层的形成，该影响层中的合金元素分布特征与合金基体的合金元素分布特征存在明显差异。1100 ℃下形成的影响层厚度大于980 ℃下的影响层厚度。tcp相的析出促使tcp相周围的γ相转变为γ′相。

Abstract:

In-situ tensile tests were conducted on a chemically corroded third-generation single-crystal superalloy DD9 at 980 and 1100 ℃. The phase transformation in the surface areas during the tensile process was analyzed using field emission scanning electron microscope, energy dispersive X-ray spectroscope, electron probe X-ray microanalysis, and transmission electron microscope. The phase transformation mechanism on the surface and the influence mechanism were studied through observation and dynamic calculation. During tensile tests at elevated temperatures, chemical corrosion promotes the precipitation of topologically close-packed (tcp) μ phase and σ phase on the alloy surface. Both the precipitation amount and size of these two phases on the surface at 1100 ℃ are greater than those at 980 ℃. The precipitation of tcp phase on the alloy surface results in the formation of an influence layer on the surface area, and the distribution characteristics of alloying elements are significantly different from those of the substrate. The depth of the influence layer at 1100 ℃ is greater than that at 980 ℃. The precipitation of tcp phase prompts the phase transition from γ phase to γ′ phase around the tcp phase.