介观尺度成分偏析对核电大型锻件显微组织与力学性能的影响机制

Heavy forgings are critical components of the nuclear power plants, the segregation of forgings become more and more serious with volume increment, which leads to not only decrement of microstructure stability but also a sharp deterioration of mechanical property of heavy forgings. In this program, the nuclear power pressure vessel steel (ASME SA508 Gr.3 steel) with the typical mesoscale segregation characteristics sampling from shell forgings will be researched, the multi-scale (segregation, grain size, phase, grain boundary) macrostructure / microstructure during heat treatment will characterized by three-dimensional reconstitution methods. Besides, the project is proposed to develop the in-situ mechanical tests, to find out the critical structures which have important influence on crack initiation and propagation. The effect of segregation (morphology, size and degree) and sample direction to the mechanical properties of the steel will be carrying out by instrumented impact test and fracture characterization, the relationship of segregation and mechanical properties deterioration in pressure vessel steel will be set up. All the works above can be used to put forward the property oriented segregation tolerance principles and heat treatment technical progress of heavy forgings.

大型锻件是新型核电装备的核心构件，其内部的成分偏析随体积的增大愈加严重，这不仅使大型锻件的组织稳定性下降，还导致其力学性能急剧恶化。本项目以具有介观尺度成分偏析特征的核电压力容器用SA508 Gr.3钢为研究对象，研究成分偏析在热处理过程中的演变规律及其对显微组织的影响，建立基于多尺度三维表征的材料成分偏析和显微组织评价规范。研究成分偏析程度及取样方向对材料力学性能的影响规律，结合能量可控的示波冲击实验和原位力学性能测试，探明影响材料微裂纹萌生与扩展的关键特征结构及其与成分偏析间的关系；构建热处理工艺-成分偏析-显微组织-裂纹特征-冲击性能间的关联，揭示介观尺度成分偏析影响核电大型锻件力学性能的机理。为以性能为导向的核电大型锻件成分偏析调控和热加工工艺优化提供科学依据。

本项目以具有介观尺度成分偏析特征的核压力容器用SA508 Gr.3钢为研究对象，研究成分偏析在热处理过程中的演变规律及其对显微组织均匀性的影响，建立了基于多尺度三维表征的材料成分偏析和显微组织评价规范。.研究了成分偏析程度及取样方向对材料力学性能的影响规律，结合能量可控的示波冲击实验和原位力学性能测试，探明了影响材料微裂纹萌生与扩展的关键特征结构及其与成分偏析间的关系；构建了热处理工艺-成分偏析-显微组织-裂纹特征-冲击性能间的关联，揭示了介观尺度成分偏析影响核电大型锻件力学性能的机理，发现了工程材料介观偏析对材料力学性能影响的尺寸效应和应变速率效应。为以性能为导向的核电大型锻件成分偏析调控和热加工工艺优化提供了科学依据。.项目研究得到了核电大型锻件成分偏析和热加工工艺的容限与达限准则，获得了锻后热处理高温扩散退火的触发条件和终止条件，该方法已成功应用于上海电气上重铸锻有限公司核电大型锻件生产中，获得合作单位好评，为推动核电大型锻件的稳健制造提供了必要的技术支撑。