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

技术支持：该研究将结合联合收割机工艺参数的变化与新的和详细的原子尺度表征，定量分析，建模和模拟的热稳定性和松弛行为的微观结构和残余应力的表面处理的航空发动机合金的研究。将获得新的见解如何在先进的表面处理，如激光冲击喷丸（LSP）和后处理退火原子配置的变化发生和相关的热力学，动力学，结构，机械，机械和建模功能。该计划是与GE基础设施航空（GEIA）和LSP技术（LSPT）合作开发的。其主要目标是确保高温和热循环对材料行为和LSP等工艺产生的性能的影响所需的基础知识，从而推进高温材料先进表面处理工艺的科学和应用基础。研究内容包括：（1）典型镍基航空发动机合金的激光冲击强化（LSP）处理：（2）采用新的方法表征表面和亚表面的宏微观残余应变/应力和显微组织变化与LSP工艺参数的关系;（3）热稳定性和残余应力松弛的测定（宏观和微观）和微观结构在高温下随时间的演变以及松弛动力学的建模：4）开发用于建立LSP对残余应力分布的影响的鲁棒建模和仿真方法;（5）将研究计划与本科/研究生教育和推广计划相结合。一个强大的表征工具库将被用来揭示材料的行为。除了传统的X射线衍射外，还将使用APS/ANL、NSLS/BNL和SSRL的设施进行深度分辨SXRD测量，以表征近表面和次表面的残余应变/应力和冷加工程度。将研究在选定温度下作为时间函数的宏观和微观残余应变/应力和微观结构稳定性的热松弛，并从所获得的数据中建模松弛动力学。将进行有限元建模以模拟LSP效应并预测残余应力及其演变。各种研究结果的相关性将为LSP和热效应等工艺产生的结构，机械，机械和性能特征提供所需的基本新见解，以将其应用扩展到高温材料应用。非技术性：LSP是一种新兴的表面处理技术，如低塑性抛光，已显示出为工程材料提供运输，推进和能源密集型系统中先进结构应用所需的非凡环境温度特性的潜力。虽然LSP等处理在高温下增强性能的潜力也明显存在，但需要进行更多的基础研究，以建立对微观结构和应力的热稳定性的基于科学的机械理解，以将这些类型的工艺扩展到高温状态。该计划的更广泛的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，如高温结构应用的LSP，刺激我们的年轻人攻读博士学位，培养一批新的科学家/工程师，为材料领域的高级职业生涯提供更好的培训。

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.