闪速加热对高强韧冷轧带钢组织与性能的影响机理

Combining the flash heating technology with the traditional processing routes of TRIP and Q&P steels, the non-equilibrium microstructure evolution during the whole flash annealing process will be investigated, and toughening and strengthening mechanism of the resultant heterogeneous microstructure will also be studied in details. In order to develop the theory of austenite formation during flash heating, the competitive mechanism of ferrite recystallization, spheroidization and dissolution of cementite, austenite formation and alloying elements partitioning needs to be revealed. The microstructure evolution and alloying elements partitioning/segregation behavior during bainite transformation for TRIP steel and quenching-partitioning process for the Q&P steels from the starting heterogeneous austenite will be critically analyzed. An integrated computational model combining GEB (Gibbs Energy Balance at the interface) model and phase filed theory will be developed for alloy design and process parameters optimization of the flash heated TRIP and Q&P steels. Finally, mechanism of strain induced martensite transformation of the heterogeneous retained austenite and its effects on the work hardening behavior will be systematically investigated, and the link between microstructure and mechanical properties will be built in order to unveil the strengthening and toughening mechanism of flash heated TRIP and Q&P steels. This project will shed new light on physical metallurgy of flash heat treatment and provide fundamental guide for its future industrialized application.

本项目拟将闪速加热与传统冷轧TRIP和Q&P钢工艺相结合，围绕闪速加热条件下全流程非平衡微观组织演变行为、非均质组织的强韧化机理等关键科学问题开展研究，阐明闪速加热条件下铁素体再结晶、渗碳体球化溶解、奥氏体相变、元素配分等物理过程的竞争机制，形成闪速加热条件下的奥氏体相变控制技术；探索非均质奥氏体在贝氏体相变与Q&P过程中的微观组织演变与元素配分/偏聚机理；在相变机制复杂、工艺参数多变的条件下，建立基于申请人提出的界面处自由能守恒理论（GEB）的相场模型，实现闪速加热TRIP和Q&P钢微观组织的集成计算与设计；阐明闪速加热TRIP/Q&P钢非均质微观组织的强韧化机理，明确不同类型残余奥氏体的相变增塑的触发机制，建立复杂微观组织与力学性能间的内在关联。该研究成果将进一步丰富闪速热处理物理冶金学理论，为闪速加热的工业化应用提供理论和实验依据。

闪速加热是新一代材料热处理技术，具有高效率、低污染等优点。本项目将闪速加热技术应用到三种先进高强钢（相变诱导塑性TRIP钢，淬火-配分钢以及中锰钢），围绕闪速加热条件下全流程非平衡微观组织演变行为、非均质组织的强韧化机理等关键科学问题开展研究，具体取得以下结果：阐明了闪速加热条件下铁素体再结晶、渗碳体球化溶解、奥氏体相变、元素配分等物理过程的竞争机制，形成闪速加热条件下的奥氏体相变控制技术；探索了非均质奥氏体在贝氏体相变与Q&P过程中的微观组织演变与元素配分/偏聚机理，采用相场模型，计算模拟了闪速加热Q&P钢非平衡微观组织演变和元素配分，揭示闪速加热TRIP和Q&P钢的亚稳奥氏体和微观组织形成机理；初步阐明了闪速加热Q&P钢非均质微观组织的强韧化机理，明确具有化学不均匀性的亚稳奥氏体的相变增塑机制，探索了复杂微观组织与力学性能间的内在关联；提出了一种新型的闪速加热-奥氏体逆转变（Flash-ART）工艺，加速了奥氏体逆转变动力学，并制备出了具有核壳结构的亚稳奥氏体,提升了核壳结构奥氏体的整体热稳定性，从而提高了中锰钢中亚稳奥氏体的含量；提出了一种高效的闪速退火工艺，在冷轧中锰钢中获得了大量亚稳奥氏体和再结晶/未再结晶铁素体的异质组织。和传统中锰钢相比，闪速退火中锰钢的非均质铁素体基体提高了其屈服和抗拉强度，同时大量的具有合适机械稳定性的亚稳奥氏体保证了良好的均匀延伸率；本项目研究成果将进一步丰富闪速热处理物理冶金学理论，为闪速加热的工业化应用提供理论和实验依据。