基于应变诱发塑性效应的新一代高强钢QP980激光焊接接头微区多相本构及组织性能演变

Based on the major demand for vehicle lightweight technology and the problems existing in the laser welding of the new generation of Quenching and Partitioning QP980 steel, the special scientific problems in the process of QP980 laser welding are studied by means of experimental research, numerical simulation and theoretical analysis. The Gleeble Thermo physical experiment machine was used to simulate the micro area of welded joint heat affected zone under the thermal cycle of welding, and the stress strain curves of micro area was measured by micro mechanical testing machine, thus the physical model of heat affected zone was established. Based on the quantitative relationship between the volume fraction of retained austenite and deformation quantity of the heat affected zone and base material, combined with the basic theories of O-C theory, residual austenite and martensitic transformation kinetics, a multi-phase constitutive model including TRIP effect was established. The electrical damage method was used to study the relationship of alternating load-crack length-resistance of QP980 laser welded joint, combining In-situ observation for micro crack propagation path on synchrotron radiation SR-CT, thus the damage mechanism of QP980 laser welded joint under alternating load was analyzed from the macro and meso scale. On the basis of the above research, the third generation high strength steel QP980 laser welding and forming process are optimized and the quality control criterion of QP980 laser welding is put forward. The results of the project will provide technical support for the industrial application of QP980.

基于汽车轻量化技术重大需求和新一代淬火-配分QP980高强钢激光焊接存在的问题，采用试验研究、数值仿真和理论分析相结合的方法对QP980激光焊接过程中特有科学问题开展研究。采用Gleeble对焊接热循环下接头热影响区微区进行热物理模拟，并评估微区应力-应变特征，建立激光焊接接头热影响区物理模型。基于热影响区微区和母材残余奥氏体体积分量与变形量的定量关系，结合O-C理论、残余奥氏体和马氏体相变动力学等基本理论，建立包含TRIP效应的多相本构建模。采用损伤电测法探索QP980激光焊接接头交变载荷-裂纹长度-电阻量的关联性，结合同步辐射SR-µCT微观裂纹扩展路径原位观测，从宏观和细观尺度上分析交变载荷下接头损伤机理。在上述研究的基础上，实现第三代高强钢QP980激光焊接及成形工艺优化和提出QP980激光焊接质量控制准则。项目研究成果将为第三代高强钢QP980的产业化应用提供技术支持。

针对国产新一代淬火配分钢QP980激光焊接过程产生的实际问题，采用试验研究、数值仿真和理论分析相结合的方法对QP980激光焊接过程中特有科学问题开展研究。本项目系统地研究了QP980激光焊接头热影响区各微区的微观组织特征及相变机理，并采用K型热电偶采集了激光焊接接头热影响区各微区的温度变化曲线，随后利用Gleeble对焊接热循环下接头热影响区微区进行热物理模拟，并评估微区应力-应变特征，建立激光焊接接头热影响区物理模型，为QP980激光焊接接头的有限元仿真提供数据支撑。基于热影响区微区和母材残余奥氏体体积分量与变形量的定量关系，分析QP980激光焊接接头中残余奥氏体的转变过程，建立包含TRIP效应的多相本构建模。测试了QP980激光焊接头的板材成形性能，并分析其断裂机理。在上述研究的基础上，实现第三代高强钢QP980激光焊接及成形工艺优化和提出QP980激光焊接质量控制准则。项目研究成果将为第三代高强钢QP980的产业化应用提供技术支持。