Evaluation of Intergranular Liquid Phase Distribution and Its Relationship to Hot Cracking

实验计划是表征晶界 化学的一系列铌轴承镍合金，然后熔化 并通过快速加热和冷却来重新固化这些边界 钨极电弧焊的典型周期。 液体化学， 液相分布（LPD）和液相体积分数 将在加热期间的选定温度下测定， 降温 液体的固化行为将是 其特征在于其共晶温度或固相线温度， 其最终固化产物，通常为Laves相。 这种行为与平衡态的偏差将是 通过与等温处理进行比较来确定。 热 开裂敏感性将通过测量 使用热延展性测试测量延展性温度。 拟议的研究将提供有关几个方面的信息。 基本问题和技术问题。 它将展示洛杉矶警察局 在非平衡阶段的冷却过程中， 热循环通过其对扩散的控制来决定LPD。 它将确定晶界化学的作用 晶间液相化学，液相体积，液相扩散 分数和LPD。 它还将显示这些之间的相关性， 在镍合金如718中的晶间热裂纹 燃气涡轮机喷气发动机的关键材料。

The experimental plan is to characterize the grain boundary chemistry of a series of Nb-bearing nickel alloys and then melt and resolidify these boundaries using a rapid heating and cooling cycle typical of a tungsten-arc weld. The liquid chemistry, liquid phase distribution (LPD), and volume fraction of liquid will be determined at selected temperatures during heating and cooling. The solidification behavior of the liquid will be characterized in terms of its eutectic or solidus temperature and its terminal solidification products, typically a Laves phase. The deviation of this behavior from equilibrium will be determined by comparison to isothermal treatments. The hot cracking susceptibility will be determined by measuring the nil ductility temperature using a hot ductility test. The proposed research will provide information on several fundamental and technical issues. It will show how the LPD evolves during the nonequilibrium stage cooling and how the thermal cycle dictates the LPD through its control of diffusion. It will identify the role of grain boundary chemistry on intergranular liquid phase chemistry, liquid phase volume fraction, and LPD. It will also show the correlation of these to intergranular hot cracking in nickel alloys such as 718, a critical material in gas turbine jet engines.