Tree-ring formation during vacuum arc remelting of INCONEL 718: Part I. Experimental investigation
Tree-ring formation during vacuum arc remelting of INCONEL 718: Part I. Experimental investigation
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INCONEL 718 真空电弧重熔过程中年轮的形成：第一部分：实验研究
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
M. Mclean
中科院分区：
文献类型：
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作者：
X. Xu;R. M. Ward;M. Jacobs;P. D. Lee;M. Mclean
在涡轮机盘的生产中，最终锻造结构关键地取决于在开坯和锻造之前通过真空电弧重熔（VAR）产生的锭晶粒结构的方面。研究了镍基高温合金INCONEL 718中铸态晶粒组织的变化，重点关注等轴晶粒串打断以柱状枝晶为主的组织的区域。这些特征，称为“树环”，形成同心圆，可以在VAR锭的蚀刻横截面上视觉观察到。这些结构是令人感兴趣的，因为它们与过程控制中的扰动相关，并且还与缺陷的发生相关。本文介绍了这些树的年轮，这两个特点，并探讨其形成的可能机制的实验研究。在宏观的热量，质量和动量传递，这可能会增加在糊状区前（类似于一个柱状到等轴过渡）的晶粒成核的波动，被认为是最有可能的假设的机制。在第二篇文章中，开发了一个多尺度数学模型来量化这些概念，并确定它们是否占观察到的功能。
In the production of turbine discs, the final wrought structure is critically dependent on aspects of the ingot grain structure produced by vacuum arc remelting (VAR) prior to cogging and forging. Variations in the as-cast grain structure in the nickel-based superalloy INCONEL 718 were investigated, focusing upon regions where strings of equiaxed grains interrupt a predominately columnar-dendritic structure. These features, termed “tree rings,” form concentric circles that can be observed visually on etched transverse sections of the VAR ingot. These structures are of interest because they correlate with perturbations in control of the process and have also been associated with the occurrence of defects. This article describes an experimental study of these tree rings, which both characterizes them and investigates possible mechanisms for their formation. Fluctuations in the macroscopic heat, mass, and momentum transfer, which can increase the grain nucleation at the mushy zone front (similar to a columnar-to-equiaxed transition), were considered to be the most likely of the mechanisms hypothesized. In a second article, a multiscale mathematical model is developed to quantify these concepts and to determine whether they account for the features observed.