Effects of High Current Density Impulses on the Properties and Microstructure of Nickelbase Superalloys

该研究项目的目标是分析高电流脉冲对镍基高温合金的显微组织和机械性能的影响。首次研究表明，两种单晶镍基合金（SC-16和CMSX-4）的塑性变形显着低于屈服强度，而暴露于高电流密度脉冲。此外，该效果取决于材料的预先蠕变变形程度。镍基高温合金PWA-1480经同样变形后，位错排列和元素分布发生了显著变化。这两种效应表明蠕变变形镍基高温合金的一种再生效应。这种再生效果将在预定的研究项目期间进行分析。在第一步中，将对两种不同的镍基高温合金在初始状态和蠕变变形状态下进行低于屈服强度的压缩试验，并提供高电流密度脉冲。然后分析枝晶、位错结构和元素分布的变化。为了验证这些微观结构变化的研究，将介绍一种原位分析方法。在蠕变试样上施加高电流密度脉冲，随后进行蠕变试验（在Bundesanstalt für Materialforschung und -prüfung，柏林），以确定对蠕变行为的影响。此外，铝双晶在高电流密度脉冲期间将受到机械应力。目的是分析电流脉冲对面心立方金属中位错动力学的影响。最后，合成的微观结构和力学分析的结果，以及位错动力学的调查将用于更深入地了解再生效应及其可能的应用。

Objective of the intended research project is the analysis of the effect of high current impulses on microstructure and mechanical properties of nickelbase-superalloys. First investigations showed plastic deformation of two monocrystalline nickelbase alloys (SC-16 and CMSX-4) significantly below yield strength while exposed to a high current density impulse. Furthermore, the effect depended on the prior creep deformation degree of the material. Nickelbase-superalloy PWA-1480 deformed in the same way showed a significant change in dislocation arrangement and element distribution. Both effects indicate a kind of regeneration effect of creep deformed nickelbase-superalloys. This regeneration effect is to be analysed during the intended research project. In a first step, compression tests below yield strength and with supply of a high current density impulse are to be carried out for two different nickelbase-superalloys in initial and creep-deformed state. Afterwards, changes in dendritic and dislocation structure and element distribution will be analysed. To verify the study of these microstructural changes, an in situ analysis method will be introduced. Application of the high current density impulses on creep specimens and subsequent creep tests (at the Bundesanstalt für Materialforschung und -prüfung, Berlin) will be used to determine the influence on the creep behaviour. Additionally, aluminium bicrystals will be mechanically stressed during high current density impulses. Objective is the analysis of the influence of the current pulses on dislocation dynamics in face-centered cubic metals in general. Finally, a synthesis of the results of the microstructural and mechanical analyses as well as of the investigations on the dislocation dynamics will be used for a deeper understanding of the regeneration effects and its possible applications.