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Simulation of the microstructure evolution in the brazing gap during reactive air brazing II

反应空气钎焊过程中钎焊间隙微观结构演变的模拟 II

基本信息

批准号：
164190245
负责人：
Dr. Markus Apel
金额：
--
依托单位：
Access e.V.
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/164190245?language=en
关键词：
Simulation microstructure evolution brazing gap

项目摘要

For the fabrication of metal-ceramic components, "Reactive Air Brazing" (RAB) has emerged as a joining process with high potential. The mechanical properties of a reactive air brazed joint are often limited by structural changes and the formation of oxide phases at the interface between the base material and the brazing alloy. Experimental investigations of brazing joints with Ag-Cu braze alloys show that in BSCF ceramic a reaction zone may form, which is associated with the penetration of Cu-and Co-containing melt along grain boundaries. At the interface to Cr-containing steels Cu and Cr-containing oxides are found. Morphology and thickness of such reaction zones affect the failure under mechanical load.The aim of this project is to model the formation of such reaction zones and to simulate the kinetics of the microstructure evolution for reactive air brazing with Ag-Cu braze alloys quantitatively. The simulation should help to identify those processes that control the formation kinetics, e. g. diffusive transport of oxygen or cupper, or the mobility of phase boundaries. A semi-quantitative understanding of the microstructure formation may lead to new ideas how the thickness of the undesired reaction zones can be influenced by a change in the alloy composition or the process conditions, e.g. by applying different oxygen partial pressures.In the model development results from the first phase of the project can be used. So far, the effect of the oxygen intake on phase formation and solidification kinetics of Ag-Cu braze alloys could be simulated quantitatively. The phase-field model has been extended to calculate DSC traces. This allows a quantitative comparison between the simulated microstructure evolution and measured DSC scans. Furthermore, computer-aided thermodynamics and the phase-field method will be used.In particular, the following points will be addressed: Simulation of the melting process and accompanied phase formation for the braze alloy, the interaction between the liquid braze alloy and BSCF ceramic, as well as reaction and phase formation at the interface between the molten Ag-Cu alloy and Cr-containing steel. A comprehensive thermodynamic database is not available for the materials involved. Based on available literature data and appropriate approximations a simplified thermodynamic description shall be developed and calibrated using the experimental results of the project partners. Thus, this project also provides a methodological contribution towards a thermodynamic approach for the modeling of joining processes for dissimilar materials.

对于金属-陶瓷元件的制造，“反应空气钎焊”(RAB)是一种很有潜力的连接方法。反应空气钎焊接头的力学性能往往受到结构变化和母材与钎焊合金界面处形成的氧化相的限制。对银铜钎焊接头的试验研究表明，在BSCF陶瓷中可以形成一个反应区，这与含铜和含钴的熔体沿晶界的渗透有关。在含铬钢的界面上发现了含铜和含铬的氧化物。这些反应区的形态和厚度影响机械载荷作用下的失效，本课题的目的是模拟这些反应区的形成，并定量模拟Ag-Cu钎料反应空气钎焊过程中微观组织演变的动力学过程。模拟应该有助于识别那些控制形成动力学的过程，例如氧气或铜的扩散传输，或相界的流动性。对微观结构形成的半定量了解可能会导致新的想法，即合金成分或工艺条件的变化如何影响不需要的反应区的厚度，例如通过施加不同的氧分压。在模型中，可以使用项目第一阶段的开发结果。到目前为止，可以定量模拟吸氧量对银铜钎料相形成和凝固动力学的影响。相场模型已扩展到计算DSC迹线。这使得可以在模拟的微观结构演变和测量的DSC扫描之间进行定量比较。此外，还将使用计算机辅助热力学和相场法，特别是以下几个方面的内容：钎料熔化过程和伴生相形成的模拟，液态钎料与BSCF陶瓷的相互作用，以及银铜合金熔体与含铬钢界面的反应和相形成。对于所涉及的材料，没有全面的热力学数据库。根据现有的文献数据和适当的近似值，应制定简化的热力学描述，并使用项目合作伙伴的实验结果进行校准。因此，该项目还为采用热力学方法模拟不同材料的连接过程提供了方法学上的贡献。