Characterization of constitutional liquid film migration in nickel-base alloy 718
Characterization of constitutional liquid film migration in nickel-base alloy 718
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DOI：
10.1147/rd.445.0668
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发表时间：
1996-09
期刊：
影响因子：
--
通讯作者：
V. L. Acoff;R. Thompson
中科院分区：
文献类型：
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作者：
V. L. Acoff;R. Thompson
当多相合金被快速加热时，有可能导致相之间的界面熔化。如果在熔化过程中，整体成分处于相图的非液态区域，但熔析相之间的联络线穿过液态区域，则称之为成分熔析。在组成熔析过程中产生的液体可以沿着晶界扩散并促进液膜迁移（LFM）。这被称为构成液膜迁移（CLFM），其在化学上类似于液膜迁移;然而，在机械上存在显著差异。镍基合金718已被研究，以显示迁移的特点，是独特的CLFM。实验包括对718合金棒进行热处理，以促进碳化铌颗粒在晶界上的捕获。然后，这些样品进行等温处理高于其组成液化温度，产生CLFM的晶界。的液体膜远离其曲率中心的运动，形成一个新的固溶体后面的迁移的液体膜，和迁移的液体膜的曲率的反转证实，CLFM是观察到的现象。迁移的液体膜的固相线温度以下的等温处理后面的铌的浓度被证明是大于在基体中的铌浓度。高于固相线温度，铌浓度没有增加。讨论了718合金中CLFM驱动力的相干应变假设的有效性。
When multiphase alloys are rapidly heated, it is possible to cause melting of the interface between phases. This is called constitutional liquation if, during melting, the bulk composition is in a nonliquid region of the phase diagram but the tie-line between the liquating phases passes through a liquid region. The liquid produced during constitutional liquation can spread along grain boundaries and promote liquid film migration (LFM). This is known as constitutional liquid film migration (CLFM), which is thermodynamically similar to liquid film migration; however, mechanistically there are significant differences. Nickel-base alloy 718 has been studied to show the features of migration that are unique to CLFM. Experimentation consisted of heat-treating rods of alloy 718 to promote the trapping of niobium carbide particles on the grain boundaries. These samples were then subjected to isothermal treatments above their constitutional-liquation temperature, which produced CLFM of the grain boundaries. The movement of the liquid films away from their centers of curvature, the formation of a new solid solution behind the migrated liquid films, and the reversals of curvature of the migrated liquid films confirmed that CLFM was the phenomenon observed. The concentration of niobium behind the migrated liquid films for isothermal treatments below the solidus temperature was shown to be greater than the niobium concentration in the matrix. Above the solidus temperature, there was no increase in niobium concentration. The validity of the coherency strain hypothesis as the driving force for CLFM in alloy 718 is discussed.