Mechanisms Governing the Thermal Stability of Microstructure and Residual Stress in Surface Treated Aero Engine Alloys

技术：这项研究将把工艺参数变化与新颖和详细的原子尺度表征、定量分析、建模和模拟相结合，研究表面处理的航空发动机合金组织和残余应力的热稳定性和松弛行为。在激光冲击喷丸(LSP)和后处理退火等高级表面处理过程中，原子构型如何发生变化，以及相关的热力学、动力学、结构、机械、机械和建模特征，将获得新的见解。该项目是与通用电气基础设施航空公司(GEIA)和LSP技术公司(LSPT)合作开发的。主要目标是确保获得所需的基本知识，了解高温和热循环对材料行为和由LSP等工艺产生的性能的影响，从而促进高温材料先进表面处理工艺的科学和应用基础。该研究计划的主要内容是：1)典型镍基航空发动机合金的LSP加工；(2)使用新方法表征表面和亚表面宏观和亚表面的宏观和微观残余应变/应力和微观结构随LSP工艺参数的变化；(3)测定高温下残余应力(宏观和微观)的热稳定性和松弛以及组织随时间的演变，并对松弛动力学进行建模；4)开发稳健的建模和模拟方法以确定LSP对残余应力分布的影响；以及5)将研究计划与本科生/研究生教育和推广计划相结合。将使用一系列强大的角色化工具来揭示材料的行为。除常规的X射线衍射仪外，还将使用APS/ANL、NSLS/BNL和SSRL的设施进行深度分辨的X射线衍射仪测量，以表征近表面和亚表面的残余应变/应力和冷加工程度。将研究宏观和微观残余应变/应力的热弛豫以及选定温度下的微观结构稳定性随时间的变化，并根据所获得的数据模拟松弛动力学。有限元模拟将模拟LSP效应，并预测残余应力及其演化。各种研究结果的相互关联将为LSP和热效应等过程产生的结构、机械、机械和性能特征提供必要的基本新见解，以将其应用于高温材料应用。非技术性：LSP是一种新兴的表面处理技术，类似于低塑性抛光，已显示出为工程材料提供运输、推进和能源密集型系统中的高级结构应用所需的一组非凡的环境温度特性的潜力。虽然像LSP这样的处理方法显然也存在提高高温性能的潜力，但还需要更多的基础研究，以建立对微观结构和应力的热稳定性的科学和机械理解，以将这些类型的过程的使用扩展到高温区域。该计划的更广泛影响还包括帮助工业和政府实验室的科学家开发和实施先进的表面处理工艺，如用于高温结构应用的LSP，激励我们的年轻人攻读博士学位，以及培养受过更好培训的新型科学家/工程师，以便在材料领域从事更高级的职业。

TECHNICAL: The research will combine process parameter variations with novel and detailed atomic-scale characterization, quantitative analysis, modeling and simulation in a study of the thermal stability and relaxation behavior of microstructure and residual stress in surface-treated aero engine alloys. New insight will be gained into how changes in atomic configurations during advanced surface treatments like laser shock peening (LSP) and post-process annealing take place and the associated thermodynamic, kinetic, structural, mechanical, mechanistic and modeling features. The program has been developed in collaboration with GE Infrastructure Aviation (GEIA) and LSP Technologies (LSPT). The primary goal is to secure the required fundamental knowledge of the impact of high temperatures and thermal cycling on materials behavior and properties generated by processes like LSP and thereby advance the science and application base of advanced surface treatment processes to high temperature materials. The key elements of the research program are: 1) LSP processing of typical Ni-base aero engine alloys; (2) characterization of surface and sub-surface macro and micro residual strains/stresses and microstructural changes as a function of LSP process parameters using novel methods; (3) determination of thermal stability and relaxation of residual stresses (macro and micro) and microstructure evolution with time at high temperatures and modeling of the kinetics of relaxation; 4) developing robust modeling and simulation approach for establishing the effect of LSP on the residual stress distributions; and 5) integrating the research program with undergraduate/graduate education, and with outreach programs. An arsenal of powerful characterization tools will be used to disclose materials behavior. Apart from conventional XRD, depth-resolved SXRD measurements will be performed using the facilities at the APS/ANL, NSLS/BNL and SSRL to characterize the near- and sub-surface residual strains/stresses and degree of cold work. Thermal relaxation of both macro and micro residual strains/stresses and microstructure stability at selected temperatures as a function of time will be studied and the kinetics of relaxation modeled from the data obtained. Finite element modeling will be conducted to simulate the LSP effects and predict residual stresses and their evolution. Correlation of the results from the various studies will provide the required fundamental new insight into the structural, mechanical, mechanistic and property features generated by processes like LSP and thermal effects to extend their use to high temperature materials applications. NON-TECHNICAL: LSP is an emerging surface treatment technology like low plasticity burnishing that has shown the potential to provide engineering materials with the extraordinary set of ambient temperature properties required for advanced structural applications in transportation, propulsion and energy-intensive systems. While the potential for enhancement of properties at high temperatures with the treatments like LSP also clearly exists, much more fundamental research is needed to establish the science-based, mechanistic understanding of the thermal stability of microstructure and stress to extend the use of these types of processes to the high temperature regime. The broader impacts of the program also include aiding scientists in industry and government laboratories in the development and implementation of advanced surface treatment processes like LSP for high temperature structural applications, stimulating our youth to pursue doctoral studies and cultivating a new breed of scientists/engineers much better trained for advanced careers in the materials field.