Beta Fleck and Segregation in Titanium Alloy Ingots
Beta Fleck and Segregation in Titanium Alloy Ingots
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钛合金锭中的 Beta 斑点和偏析
DOI：
10.1515/htmp.2006.25.5-6.337
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发表时间：
2006
影响因子：
1.5
通讯作者：
S. Cockcroft
中科院分区：
文献类型：
--
作者：
A. Mitchell;A. Kawakami;S. Cockcroft
在大多数钛的β和α/β合金中，工业上称为“β斑点”的偏析缺陷发生在最终真空电弧重熔（VAR）铸锭凝固期间的偏析中。在这项工作中，我们使用本研究的第一部分中生成的数据来调查缺陷的可能原因。我们的结论是，不止一个机制是潜在的运作。在高度合金化的材料中，缺陷机制可能是由与钢和超合金中的“雀斑”缺陷相似的流动系统引起的：在较低合金化的材料中，更可能的是，缺陷出现在大VAR最终铸锭液池体积中的等轴晶体的再分布中，该体积在低温度梯度下凝固。在任一情况下，该问题的工业实用解决方案似乎在于在固化界面处具有更陡温度梯度的VAR熔化。我们还概述了合金设计的未来需要，以考虑到不同的β稳定元素的合金配方的缺陷形成潜力的差异。
The segregation defect known industrially as "betafleck" occurs in most of the beta and alpha/beta alloys of titanium, arising in segregation during the solidification of the final vacuum arc remelted (VAR) ingot. In this work we use the data generated in Part I of this study to investigate the possible causes of the defect. We conclude that more than one mechanism is potentially operative. In highly alloyed material the defect mechanism is likely to be caused by a similar flow system to that responsible for the "freckle" defect in steels and superalloys: in the lower alloyed materials, it is more likely that the defect arises in the redistribution of equiaxial crystals in the large VAR final ingot liquid pool volume which is solidifying under low temperature gradients. In either case, the industrially-practical solution to the problem appears to lie in VAR melting with steeper temperature gradients at the solidifying interface. We also outline the future need for alloy design to take into account the difference in defect-forming potential of the different betastabilizing elements available for alloy formulation.