耦合冷却历史的微观组织演变数值建模与仿真研究

The microstructure evolution process and results of metal materials during heat treatment partly decide the macroscopic mechanical properties of parts in processing and using process, accurate prediction of microstructure evolution is of great significance for the optimization design of process and structure of parts. For the microstructure evolution of multiphase materials, many researches indicate that the alloy element concentration in remaining austenite and the pre-eutectoid microstructure have important influence on the subsequent decomposition of remaining austenite. However, until now, most of the research focus just on the influence of current temperature and fraction of each microstructure, less on the influence of cooling history path, to the numerical simulation of microstructure evolution. This project will adopt the research method of combining experiment and simulation, the dual-phase steels of ferrite/bainite will take as the research object, and the influence of cooling history on microstructure evolution will be investigated, by the designed heat treatment experiments with special cooling history, the corresponding relationship between cooling history and microstructure evolution will be established. And then, a calculated model of microstructure evolution considering the influence of cooling history, by introducing the influence parameters to calculated model, will built, it can provide theoretical guidance for the prediction of microstructure evolution in heat treatment process, and promote the development of current calculated theory of microstructure evolution. Finally, the subroutine about the calculation of microstructure evolution of material will development, by using the interface for further development based on finite element software, and the finite element simulation platform will set up for providing a simulation tool to the optimization design of hot working technology of metallic materials.

金属材料热处理过程微观组织演变历程和最后构成在一定程度上决定了零件的加工和服役状态下宏观力学性能，准确的微观组织演变预测对零件加工工艺和尺寸结构优化设计有重大意义。对于多相材料微观组织演变，已有研究发现，剩余奥氏体合金元素浓度和先共析析出组织对后续奥氏体分解有重要影响。但目前，对于微观组织演变数值模拟研究上仅关注当前温度和组织份数，而对冷却历史影响研究较少。本项目拟采用物理实验和仿真建模相结合的研究方法，以铁素体/贝氏体双相钢（G18CrMo2-6）为研究对象，设计特殊冷却路径的热处理实验，研究冷却历史对微观组织演变的影响，建立对应关系，引入影响参量，构建耦合冷却历史的微观组织演变数值计算模型，为热处理过程微观组织演变的预测提供理论指导，推动微观组织演变数值计算理论的进一步发展；开发基于有限元软件的材料计算子程序，搭建有限元仿真平台，为金属材料热加工工艺优化设计提供仿真工具。

金属材料热处理过程微观组织演变历程和最后构成在一定程度上决定了零件的加工和服役状态下宏观力学性能，准确的微观组织演变预测对零件加工工艺和尺寸结构优化设计有重大意义。在本基金项目的支持下，开展了如下工作：首先，以铁素体/贝氏体双相钢（G18CrMo2-6）为研究对象，设计特殊冷却路径的热处理实验，开展了大量微观组织演变实验，获得了有效微观组织演变实验数据；然后，基于所获得不同冷却历史下微观组织演变实验数据，研究冷却历史对微观组织演变的影响，引入了等效碳浓度参量和先共析铁素体影响参量。结合材料物理冶金模型，构建了考虑残余奥氏体内等效碳浓度和先共析铁素体份数影响的微观组织演变计算模型，最后，基于所构建的仿真模型，结合通用有限元仿真软件，开发出仿真计算子程序2个，所开发出的子程序，可以预测金属构件热处理过程微观组织演变份数，热处理变形特征和构件残余应力情况。本项目研发成果，为热处理过程微观组织演变的预测提供理论指导，推动微观组织演变数值计算理论的进一步发展；开发出的基于有限元软件的材料计算子程序，为金属材料热加工工艺优化设计提供仿真工具。