TRIP效应对中锰钢加工硬化影响机理研究

Thanks to the excellent combination of strength and ductility, TRIP-assisted medium manganese steel is becoming one of the most promising members of the automotive lightweight materials. However, the current understanding of the strain hardening mechanisms of medium manganese steel is still unclear due to its complicated microstructures. There is still a lack of systematic and in-depth research, especially for the important issue of the TRIP effect on the strain hardening mechanisms. This project intends to reveal the correlation between the TRIP effect, strain hardening properties, and the microstructures by using both the experiments and modeling methods. With the help of various in-situ characterization techniques, the evolution of microstructures with plastic deformation is well observed. Based on the dislocation theory, an assessment method to quantitatively investigate the strain hardening mechanisms in medium manganese steel is proposed. Microstructures, strain rate, temperatures and other key factors governing the TRIP effect are carefully controlled so that their multiple effects on the strain hardening can be effectively separated. Finally, a prediction model of the strain hardening properties in the TRIP-assisted medium manganese steel is well proposed, and then the optimized strategy for the TRIP effect to achieve best strain hardening is formulated. The research outcomes of this project will provide the important theoretical as well as technical guidance on the improvement of mechanical properties in the medium manganese steel. Meanwhile, the project will also help to deepen the understanding of the deformation mechanism in medium manganese steel and provide the necessary technical support for the establishment of mechanical properties prediction models under various conditions.

中锰TRIP钢因具有优异的强塑性综合机械性能，被视为极具发展潜力的汽车轻量化材料。然而因其具有复杂的微观组织结构，目前对其加工硬化变形机制的认识尚不够明确，关于TRIP效应对加工硬化的影响机理这一重要课题仍缺乏系统深入的研究。本项目拟采用实验与理论相结合的研究手段，深入探究TRIP效应、加工硬化机制及微观组织结构三者间的相互作用关系。采用多种原位表征技术获取微结构随塑性变形的演化过程信息，结合位错物理模型提出对中锰钢加工硬化机理的定量评估方法。通过对微组织结构、应变速率及温度等TRIP效应影响因素的精细调控，将其对加工硬化能力的多重影响有效分离，提出基于位错理论的中锰钢加工硬化预测模型，并由此尝试建立TRIP效应的最优化模型。本项目的完成有望为中锰钢强韧化改进设计提供重要的理论指导与工艺反馈，并有助于加深对中锰钢塑性变形机理的认识，为其在特殊加载条件下机械性能预测模型构建提供必要技术支持。

中锰TRIP钢因具有优异的强塑性综合机械性能，被视为极具发展潜力的汽车轻量化材料。由于中锰钢存在复杂的微观组织结构，其变形机制仍不明确。本研究拟采用实验与理论相结合的研究手段，深入研究中锰钢TRIP效应、加工硬化机制及微观组织结构三者间的相互作用关系。.由于中锰钢锰元素含量较高，在生产中容易产生成分偏析，形成偏析组织，对材料性能带来严重影响。因此，本项目开展了中锰钢锰偏析影响及其组织优化策略研究。研究发现：（1）即使是同成分同工艺中锰钢，不同锰偏析程度仍会对其TRIP效应及加工硬化带来严重差异。因此，在中锰钢相关研究中，既要关注整体元素成分比例，也要关注成分分布的影响；（2）更高锰偏析程度会加剧各相组织成分及性能的不均匀性，导致变形时部分亚稳态奥氏体提前相变，加速TRIP效应发生。因此，需根据原有中锰钢组织及性能特点建立相应的锰偏析优化策略。.为深入研究中锰钢多相组织变形机理。开展了基于原位中子散射实验的多相钢协调变形机理研究。研究发现：（1）多相钢协调变形时，过往马氏体相应力的测量难以准确评估其弹塑性变形转变阶段。因此，基于位错密度测量结果准确评估多相钢变形相变马氏体的屈服强度，对于正确建立多相TRIP钢本构模型具有关键作用。（2）结合不同多相TRIP钢实验数据，建立了基于位错理论的多相TRIP钢加工硬化模型。模型结果与多个中子散射结果及原位微观DIC结果取得了良好的一致性。并为马氏体本构关系提供了基于晶粒尺寸的近似模型。.本项目的完成有望为中锰钢强韧化改进设计提供重要的理论指导与工艺反馈，并有助于加深对中锰钢塑性变形机理的认识，为其在特殊加载条件下机械性能预测模型构建提供必要技术支持。