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在10-100μm/s的生长速度范围,热梯度为10 K/mm的情况下,研究Ni-25%Al(摩尔分数)合金定向凝固的微观结构演变规律。凝固组织显示了γ’-β平衡共晶相向γ-β亚稳态共晶加β枝晶相的转变。在25μm/s的生长速度时生成的γ’-β和γ-β共晶的混合微观组织表明转变发生在γ和γ’相之间的竞争生长期间。在凝固期间选取微观结构时应考虑各个相的生长温度,试验结果显示在给定生长速度的情况下,在凝固期间,应优先选择在最高温度固化的某个相或微观结构。而且,在25-60μm/s的生长速度范围内,由于稳态和亚稳态共晶具有相似的生长温度,因此可以共存且同时生长。
The microstructure evolution of the directional solidification of Ni-25% Al (Mo fraction) alloy was investigated at a growth rate of 10-100μm / s and a thermal gradient of 10 K / mm. The solidified tissue shows the transformation of γ’-β equilibrium eutectic to γ-β metastable eutectic plus β dendrite phase. The mixed microstructure of γ’-β and γ-β co-crystals generated at a growth rate of 25 μm / s indicates that the transition occurs during competing growth between γ and γ ’phases. The selection of microstructures during solidification should take into account the growth temperature of the individual phases and the results show that at a given growth rate, a phase or microstructure which solidifies at the highest temperature should preferably be chosen during solidification. Moreover, within the growth rate range of 25-60 μm / s, both steady-state and metastable eutectic can coexist and grow simultaneously because they have similar growth temperatures.