多尺度析出相强化Fe-Cr-Ni基铸造耐热合金的显微组织稳定性与蠕变行为研究

Heat-resistant alloys are widely used in petroleum, chemical, power generation, aerospace and other industries related to national security and the national economy. Heat-resistant alloys are always strengthened by various precipitates. The multi-scale precipitates have different thermal stability and different interactions with the alloy matrix, so the high temperature behavior of co-precipitates and their synergy effect are vital for the high temperature performance of heat-resistant alloys. In this project, the heat-resistant Fe-Cr-Ni-Nb-C alloys are designed by the CALPHAD method. The weight ratio of micron-size precopitates to nano-sized precipitates is controlled. The research focuses on the thermal stability and creep behavior the heat-resistant alloys containing hierarchical co-precipitates at 1000 and 1100 ℃. The effects on the phase transition/coarsening of precipitates as well as the interaction between precipitates and the matrix are explored. The mechanisms of hot deformation and fracture of heat-resistant alloys containing hierarchical co-precipitates are studied. The synergy effects of the hierarchical co-precipitates on the aging and creep process are revealed. The aim of this project is investigating and modeling the coarsening, strengthening and damaging effects of the heat-resistant alloys containing hierarchical co-precipitates by combining the theoretical and experimental method. The research results are important for improving the high temperature properties of cast heat-resistant Fe-Cr-Ni alloys above 1000 ℃.

耐热合金广泛应用于关系到国家安全和国民经济命脉的行业领域，构造多种析出强化相是耐热合金的主要增强手段。多尺度析出相具有不同热稳定性以及与基体不同交互效果，因此多尺度析出相的高温行为及其之间的协同作用对合金的高温服役性能具有决定影响。本项目通过相图计算方法设计Fe-Cr-Ni-Nb-C体系耐热合金成分，构造具有不同组成比例的微米级与纳米级析出相。重点研究含多尺度析出相合金在1000与1100 ℃的显微组织稳定性与蠕变行为。探明多尺度析出相相变/粗化行为以及与基体交互作用的影响因素机制。探明含多尺度析出相合金的热变形机理与断裂机理。揭示多尺度析出相在高温时效与蠕变过程中的协同效应。本项目采用理论与实验相结合的研究方案，旨在建立Fe-Cr-Ni基铸造耐热合金的析出相粗化与高温增强及损伤模型。研究成果对提升其1000 ℃以上高温服役性能具有重要意义。

离心铸造Fe-Cr-Ni耐热合金由于具有优异的高温耐蠕变和耐腐蚀性能，是石化工业中制氢转化炉和乙烯裂解炉部件的关键材料。为了满足原料适应性与节能减排的目标，石化设备的大型化与高参数化发展对Fe-Cr-Ni耐热合金的开发提出了更高要求。本研究首先结合相图计算方法与元胞自动机技术，实现了改性离心铸造25Cr35NiNb合金的关键制备工艺以及关键微合金元素的设计。其次，研究了不同含量N+C元素对改性25Cr35NiNb合金的高温显微组织演变和蠕变行为的影响，揭示了对合金多尺度富Cr相与富Nb相的含量、形态与相变过程影响规律。采用蠕变门槛应力与蠕变损伤诊断分析，结合显微组织分析阐明了位错攀移与显微组织退化分别主导的蠕变变形与蠕变失效机制。通过与传统离心铸造25Cr35NiNb合金相比，本研究开发的改性离心铸造25Cr35NiNb合金通过优化设计实现了固溶强化、析出强化和相稳定化，从而具有了优异的蠕变抗力与蠕变损伤容限综合性能。再次，通过建立包含离心铸造25Cr35NiNb合金化学成分、蠕变测试条件、铸态显微组织及其对应高温蠕变性能的材料数据库，开发了根据多源异构材料数据预测25Cr35NiNb合金蠕变断裂寿命的深度学习模型。采用多层感知器和卷积神经网络分别处理文本和视觉数据，并通过深度学习融合模型集成特征提取实现目标预测，该融合模型能够高效利用多种类型的材料表征信息，并以高通量与高鲁棒性方式建立与服役性能之间关系。综上所述，本项目重点研究的含多尺度析出相Fe-Cr-Ni基耐热合金高温组织演变、蠕变、失效行为机制及性能预测模型，为1000 ℃温度级别服役的合金设计及组织性能调控提供了新思路，建立的合金设计与评估方法也为新型耐热合金的研发提供了理论与技术支持。