基于初始组织调控的高强钢组织设计与性能优化

Austenitisation treatment plays an important role in the microstructural design and property optimization of advanced high strength steels, for obtaining proper state of austenite or retained austenite in the final microstructure. The complexity of the kinetics of austenite formation lies in the fact that it is directly affected by the condition of initial microstructures. The proposed project aims to optimize the final microstructure (mainly the morphology, size, distribution and stability of austenite) or to obtain target microstructure through the control of initial microstructures, including the control of initial distribution of carbon, initial morphology and initial dislocation density, which will affect the nucleation, transformation mechanism and growth kinetics of austenite. Advanced characterization methods will be used to investigate the transformation characteristics of austenite, properties of reversed austenite and the mechanical properties of the final microstructure. In situ Gleeble/LUMet technique will be applied to trace the austenite grain growth during austenitization, the local chemical composition in single phase or phase boundaries will be measured by 3DAPT, and the mechanical properties of reversed austenite will be analyzed with the help of in situ tensile test using synchrotron radiation XRD. The proposed research project will definitely be helpful to bring about new idea or an alternative way for the development of the next generation of high strength and ductility steels.

先进高强钢的组织设计与性能优化显著依赖于奥氏体的转变，以获得合适的母相奥氏体组织或残余奥氏体于最终组织中。奥氏体转变的复杂性在于其直接受初始组织的影响，因而至今仍被不断关注研究。本项目意在基于初始组织调控，设计起始碳元素分布、组织起始形貌、起始位错密度等，来影响奥氏体的形核、转变机制、长大等动力学过程，从而达到优化组织（针对奥氏体形貌、尺寸、分布及稳定性）或获得目标组织的目的。通过先进测试表征手段来研究奥氏体的转变特征、逆变奥氏体的单相性能及最终组织的力学性能，如原位Gleeble/LUMet技术测量奥氏体晶粒的原位长大，3DAPT测单相或相间的局域成分，原位同步辐射拉伸研究逆变奥氏体的单相机械性能等等。研究结果为下一代高强塑钢的研发提供新的设计思路。

本项目针对热成形钢（马氏体组织）、QP钢、10Ni钢（奥氏体+马氏体、奥氏体+铁素体双相组织）及中锰钢（奥氏体+铁素体双相组织），研究了初始组织（初始相分布、元素分布及轧制状态）对后续组织转变（如奥氏体转变等）、残奥量、最终组织尺寸、形貌及力学性能等的影响规律，运用高分辨透射电镜、原位同步辐射拉伸、EBSD及3DAP等先进表征手段对组织及性能进行了表征分析，并讨论了内在形变机制。通过初始组织调控优化了热成形钢的综合力学性能，获得了超高强塑异构层状组织10Ni钢，相关结果发表多篇期刊论文，达到预期目标。研究结果表明，初始组织调控对于高强钢的最终组织性能的优化具有重要作用。