淬火-配分钢配分过程中马氏体-奥氏体界面互迁移的研究

通过控制残余奥氏体，淬火-配分（Q&P）工艺可有效提高许多低碳合金钢的力学性能，已成为极具潜力的发展低成本先进钢铁材料的技术路线。精确设计Q&P工艺的先决条件是科学理论指导下的定量建模。受限于对配分过程中马氏体-奥氏体（马-奥）界面互迁移的认识不够深入，目前的定量模型还难以准确描述配分时的组织演化过程。本项目拟对Q&P钢配分前后马-奥界面进行系统的实验和理论研究，从而弥补定量建模的短板。第一步要在对淬火组织精确表征的基础上，获得对马氏体相变晶体学、马-奥界面结构和界面迁移的自洽解释。第二步将所获得晶体学知识与热力学和动力学理论相结合，建立Q&P钢配分过程马-奥界面互迁移的定量模型 （简称二步三结合建模）。相变晶体学和界面迁移的原位研究是申请团队的特长，项目研究结果可望增进对Q&P钢配分过程中马-奥界面互迁移的理解，为优化Q&P钢配分工艺提供科学依据，同时对板条马氏体相变理论发展有所贡献。

By controlling the retained austenite, Quenching & Partitioning (Q&P) heat treatment has become a highly promising technique for developing low-cost advanced steels with improved mechanical properties. A knowledge based model to describe the composition and microstructure change during the partitioning process is essential to proper design of a Q&P heat treatment. Due to the lack of in-depth understanding the mutual migration of martensite-austenite interfaces during partitioning, existing models have limited capability to provide a correct description about the microstructure evolution during partitioning. In this project, martensite-austenite interfaces before and after partitioning will be investigated both experimentally and theoretically. In the first step, martensite transformation crystallography, martensite-austenite interfacial structure in the quenched samples will be characterized using TEM, and a quantitative analysis will be made to gain a self-consistent interpretation of the observed results and to build a proper model for martensitic phase transformation. In the second step, a model combining crystallography, thermodynamics and kinetics aspects of the interface migration will be established to describe the mutual migration of martensite-austenite interfaces during partitioning in a Q&P steel. The applicant’s group has rich research experience in phase transformation crystallography and in-situ studying of interface migration. The outcome of this project will yield new insight into mutual migration of martensite-austenite interfaces for better understanding partitioning process. It will also shed light on the transformation theory of lath martensite.