一种高Mo强化Ni3Al基单晶高温合金凝固行为的研究进展

Research Development of solidification behaviors of a Mo-richNi3Al based single crystal superalloy

摘要:

与传统Ni基单晶高温合金相比，高Mo强化Ni3Al基单晶高温合金具有富Al和富Mo的成分特征，即该合金具有低密度的优势。本文总结了该合金的凝固特性，并发现高Al的成分特征显著提高了平均液相扩散系数，即Ni3Al基单晶高温合金的平均液相扩散系数为10-8 m2/s数量级，比Ni基单晶高温合金高1-2个数量级。同时，高Al和高Mo的成分特征决定了合金具有枝晶间初生γ''相和富Mo相的末期凝固行为，这与Ni基单晶高温合金的枝晶间析出物（γ/γ''共晶和γ''相）明显不同，但高Al和高Mo的成分特征对凝固特征温度的影响较小。Mo在凝固时显著偏析于未凝固的液相，该偏析行为将降低高Mo强化单晶高温合金的雀斑形成倾向。合金凝固特性的研究将为单晶制备工艺与工程应用奠定基础。

Abstract:

As compared with traditional Ni based single crystal (SC) superalloy, the composition characteristic of Mo-rich Ni3Al based SC superalloy is high Al and Mo contents, which indicated that this alloy has the advantage of low density. This work summarized the solidification characteristics of this alloy. Al was found to significantly increase the average liquid diffusion coefficient during solidification, and the liquid diffusion coefficients of Ni3Al based SC superalloys were one to two order of magnitude higher than those of Ni based SC superalloys, reached 10-8 m2/s magnitude. Meanwhile, high Al and Mo contents in experimental alloy led to the solidification of interdendritic primary γ'' phase and Mo-rich phase at the last stage of solidification, which was significantly different from the typical interdendritic precipitation of Ni based SC superalloy (γ/γ'' eutectic and γ'' phase). Moreover, the influence of high Al and Mo contents on solidification characteristic temperatures was little. Mo had the strongest tendency to segregate to interdendritic residual liquid phase during solidification of Mo-rich Ni3Al based SC superalloy, and this microsegregation behavior can decrease the tendency of freckle formation. The investigation of solidification behavior of this Mo-rich Ni3Al based SC superalloy will be beneficial for the preparation technique and industrial application for this newly developed SC superalloy.