铁基烧结体热锻过程高温流变损伤行为及断裂机理研究

The damage and fracture caused by low tensile plastic of porous sintered material is one of the key factors in hampering the development of powder forging technology. Now, the most studies are mainly focused on the effect of density on its damage and fracture during plastic forming, while the impact of hot forging process, especially temperature and rate on its damage and fracture at elevated temperature, has not been conducted in detail. In the present project, the flow and damage behaviors of P/F-10C50 sintered bodies under hot forging process condition will be investigated using the methods of experimental study, numerical analysis and finite element simulation. The mathematical models characterizing the flow and damage behaviors will be improved and evaluated by clarifying the dependence of flow and damage behavior characteristics on density, temperature and rate. The fracture mechanisms of sintered body during hot forging will be further revealed by exploring the influence of density, temperature and rate on the flow and fracture behaviors of sintered powder particles. The hot forging process of part will be optimized by finite element simulation and further tested by experiments to propose the measure for preventing damage and fracture of sintered preform during hot forging. The research results have theoretical and technical guidance for ensuring the metallurgy structural integrity of powder forged parts during hot forging and accelerating the localization process of powder forged automotive key parts, such as connecting rod and synchronizer ring.

多孔烧结材料低拉伸塑性引起的损伤断裂是制约粉末锻造技术发展的关键因素之一。目前，对其塑性成形损伤断裂的研究主要侧重于致密度的影响，而对热锻工艺因素尤其是温度和速率影响其高温损伤断裂的研究尚显不足。本项目拟以P/F-10C50铁基烧结体为研究对象，采用实验研究、数值分析和有限元模拟有机结合的方法，研究烧结体在热锻工艺条件下的高温流变和损伤特征，明晰流变和损伤特征与烧结体致密度、变形温度和应变速率之间的关系，进而完善并评估烧结体的高温流变和损伤数学模型；阐明致密度、变形温度和应变速率对烧结体内烧结颗粒流变断裂的影响机制，进一步揭示烧结体热锻过程的损伤断裂机理；将数学模型应用于粉末锻造过程的有限元模拟和优化设计，并进行实验验证，以期提出预防烧结预成形坯热锻损伤断裂的有效措施。项目研究结果可为保证粉锻零件热锻过程的冶金结构完整性，促进连杆、齿环等粉锻汽车关键零件的自主研发提供理论和技术指导。

针对目前烧结体热锻过程变形温度和应变速率影响其高温流变损伤断裂研究的不足。本项目将实验研究与数值分析和有限元模拟有机结合，系统研究了P/F-10C50铁基烧结体在热锻工艺条件下的高温流变致密化和损伤断裂行为及机理。研究成果包括：明晰了热锻工艺因素对烧结体高温流变致密化和损伤累积的定量影响和作用机理，建立了相应的流变致密化模型、损伤累积模型和损伤断裂判据，表征烧结体热锻过程的高温流变致密化和损伤断裂行为。通过烧结预成形坯闭式热锻过程的数值模拟分析和实验研究，深入揭示了预成形坯热锻过程的流动变形和致密化规律及其相互作用机制，探讨了抑制预成形坯热锻损伤断裂的方法，最终制备出无损伤缺陷、高致密度、综合力学性能优良的粉锻件。在此基础上，初步提出了预防铁基烧结预成形坯热锻过程高温损伤断裂的有效措施。相关研究成果进一步丰富了粉末烧结体高温塑性加工的致密化和损伤控制理论，为粉锻零件的热锻工艺和模具设计提供重要的理论支撑和技术指导。