Detached Melt Nucleation during Diffusion Brazing of a Technical Ni-based Superalloy: A Phase-Field Study
Detached Melt Nucleation during Diffusion Brazing of a Technical Ni-based Superalloy: A Phase-Field Study
复制标题
技术镍基高温合金扩散钎焊过程中的分离熔体形核：相场研究
DOI：
10.1088/1757-899x/84/1/012031
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
S. Piegert
中科院分区：
文献类型：
--
作者：
B. Böttger;M. Apel;B. Laux;S. Piegert
先进的凝固工艺，如焊接，钎焊和钎焊，通常以其特定的凝固条件为特征。但它们也可能包括不同类型的熔化过程，这些过程本身受到所应用材料的初始微观结构和成分的强烈影响，因此对接头的最终质量和机械性能起决定性作用。这样的熔化过程通常不被很好地理解，因为-与凝固科学的其他领域相比-到目前为止对熔化的研究相对较少。此外，关于微观结构模拟，熔化在过去一直被严重忽视，尽管由于所涉及的相的反向扩散率，该过程与凝固有很大不同。在本文中，我们进行了相场模拟，显示了使用不同含硼钎焊合金对定向凝固和热处理的高合金镍基燃气涡轮机涡轮机叶片材料进行扩散钎焊过程中金属间相的熔化、凝固和沉淀。与通常的看法相反，基础材料的熔化并不总是平面的，并且可以进一步伴随着基础材料内部的第二液相的分离成核和生长，导致凝固后接头的多晶形态。这些发现是一致的钎焊实验室样品，其特征在于通过EDX和光学显微镜的结果，并可以解释在特定的合金热力学和相互扩散动力学。讨论了对高合金材料钎焊新认识的意义.
Advanced solidification processes like welding, soldering, and brazing are often characterized by their specific solidification conditions. But they also may include different types of melting processes which themselves are strongly influenced by the initial microstructures and compositions of the applied materials and therefore are decisive for the final quality and mechanical properties of the joint. Such melting processes are often not well- understood because - compared to other fields of solidification science - relatively little research has been done on melting by now. Also, regarding microstructure simulation, melting has been strongly neglected in the past, although this process is substantially different from solidification due to the reversed diffusivities of the involved phases. In this paper we present phase-field simulations showing melting, solidification and precipitation of intermetallic phases during diffusion brazing of directionally solidified and heat-treated high-alloyed Ni- based gas turbine blade material using different boron containing braze alloys. Contrary to the common belief, melting of the base material is not always planar and can be further accompanied by detached nucleation and growth of a second liquid phase inside the base material leading to polycrystalline morphologies of the joint after solidification. These findings are consistent with results from brazed laboratory samples, which were characterized by EDX and optical microscopy, and can be explained in terms of specific alloy thermodynamics and inter-diffusion kinetics. Consequences of the gained new understanding for brazing of high- alloyed materials are discussed.