基于位错工程理念的RT Q&P-D钢变形和断裂机理研究

汽车轻量化是缓解我国环境污染及能耗的有效方法。提升淬火&配分（Q&P）钢的强度利于汽车轻量化并提高碰撞安全性。然而，使用传统强韧化方法在提高强度的同时往往损害塑性。.本项目通过位错工程理念促进室温淬火&配分（RT Q&P）钢的强度及塑性。在奥氏体形变无法有效增加RT Q&P钢奥氏体位错密度的基础上，提出配分过程中进行温轧变形，获得双相高位错密度结构，得到新型室温淬火&配分-变形（RT Q&P-D）钢。本项目研究RT Q&P-D钢的双相高位错密度结构对微观组织演变和宏观力学行为的作用机理；建立包含微观组织演变信息的物理本构模型和断裂准则，实现对RT Q&P-D钢力学行为及断裂过程的有效模拟；揭示RT Q&P-D钢的微观组织结构（层状构筑结构、高位错密度及亚稳态奥氏体）与断裂性能的定量关系。.本项目研究有助于优化Q&P钢的组织结构和力学性能，服务于第三代先进高强度钢的制备、组织优化和性能调控。

Developing lightweight structural components is an effective method to alleviate environmental pollution and energy consumption in our country. Elevating the strength of quenching and partitioning (Q&P) steel can provide extra benefits for further automobile weight reduction and improve passenger safety during crash events. However, improving the strength of Q&P steel by harnessing the conventional strengthening mechanisms frequently results in a reduced ductility, which is known as the strength-ductility trade-off in metallic materials. .The thrust of the present project is to increase the strength of room-temperature quenching and partitioning (RT Q&P) steel by using dislocation engineering concept. Based on the understanding that the deformation of austenite without decomposition (or ausforming) is not able to increase the dislocation density of austenite in RT Q&P steel, here we propose to combine the warm rolling and partitioning processes to obtain a dual-phase microstructure with high-dislocation density, enabling the development of a new room-temperature quenching and partitioning-deformation (RT Q&P-D) steel. The project will comprehensively investigate the effect of dual-phase high-dislocation density microstructure on the microstructure evolution and mechanical behavior of RT Q&P-D steel. Both physical models and fracture criterion which incorporate the microstructure evolution will be established in this project, facilitating the effective simulation of mechanical behavior and fracture in RT Q&P-D steel. The present project will thoroughly study the effect of initial microstructure such as hierarchical lamella microstructure, high dislocation density and metastable retained austenite grains on the fracture properties of RT Q&P-D steel in a quantitative way..The present investigation on the deformation and fracture mechanisms of RT Q&P-D steel developed by dislocation engineering concept will help to optimize the microstructure and mechanical properties of Q&P steel, contributing to the general understanding on the processing, microstructure and, property of 3rd generation of advanced high strength steel (AHSS).