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Evolution of type II residual strains in dependence on the microstructure of nickel base superalloys

II 型残余应变随镍基高温合金微观结构的演变

基本信息

批准号：
280883331
负责人：
Dr. Michael Hofmann
金额：
--
依托单位：
Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/280883331?language=en
关键词：
Evolution type II residual strains

项目摘要

Macroscopic residual stresses may influence the mechanical properties of industrial components strongly. Thus, the reliable analysis of residual stresses is crucial.By diffraction methods, the macroscopic residual stresses are usually determined relative to a stress-free reference sample, which is cut from the component of interest. The macroscopic relaxation of the stress state during cutting is assumed to leave the type II residual stresses (intergranular and interphase stresses) unaffected. However, particularly in high performance alloys with multiple crystallographic phases inside and which undergo complex thermo-mechanical treatments during their production process, a change of type II residual stresses during macroscopic relaxation is conceivable. In a diffractometric residual stress analysis this may cause high spurious stresses and strains, which may lead to high costs due to overestimated residual stresses and thus due to excessively designs. Our preliminary work points to the fact, that the evolution of intergranular and interphase micro strains may be governed by different microstructural mechanisms in IN718 and Haynes282. The goal of this research project is the fundamental understanding of the sources of different micro mechanical behavior of these two nickel based superalloys.The influence of different microstructural parameters (phase fractions, grain sizes, type of phases) will be studied on samples of IN718 and Haynes282 differing in microstructure due to specially designed heat treatment sequences. The characterization of the microstructure will be preformed by conventional methods as optical micrographs and scanning electron microscopy combined with different high end methods as atom probe tomography, transmission electron microscopy and neutron scattering methods. This combination provides a characterization of the microstructure over different length scales and gauge volumes. The evolution of intergranular and interphase micro strains will be done by in-situ neutron diffraction. The comparison of the microstructure before and after plastic deformation combined with the results of the in-situ tests, will help to enlighten the detailed microstructural mechanisms during plastic deformation. The influence of different microstructural parameters on the micro mechanical material behavior will be identified by this procedure. Supplementary simulations will help to describe, analyses and interpret the experimental findings.

宏观残余应力对工业零件的力学性能有很大的影响。因此，残余应力的可靠分析是至关重要的。通过衍射法，宏观残余应力通常是相对于从感兴趣的部件上切下的无应力参考样品来确定的。假设在切割过程中应力状态的宏观松弛不会影响II型残余应力(晶间应力和相间应力)。然而，特别是在内部含有多个晶相的高性能合金中，在其生产过程中经过复杂的热机械处理，在宏观松弛过程中，II型残余应力的变化是可以想象的。在衍射残余应力分析中，这可能会导致高的虚假应力和应变，这可能会由于高估残余应力而导致高成本，从而导致过度设计。我们的初步工作指出，晶间和相间微观应变的演化可能受IN718和Hayens282中不同的微观结构机制的支配。本研究项目的目的是从根本上了解这两种镍基高温合金不同微观力学行为的来源。研究不同的显微组织参数(相分数、晶粒度、相类型)对因特殊设计的热处理程序而导致组织不同的IN718和Hayens282样品的影响。微观结构的表征将通过光学显微镜和扫描电子显微镜等常规方法进行，并结合原子探针层析、透射电子显微镜和中子散射等不同的高端方法进行。这种组合提供了不同长度尺度和量规体积上的微观结构的特征。晶间和相间微观应变的演化将通过原位中子衍射来完成。对比塑性变形前后的显微组织，结合现场试验结果，将有助于揭示塑性变形过程中详细的微观组织机理。不同的微观结构参数对材料微观力学行为的影响将通过这一过程来识别。补充模拟将有助于描述、分析和解释实验结果。