权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Consistent physically-based modeling of dynamic recrystallization under hot working conditions

热加工条件下动态再结晶的一致物理建模

基本信息

批准号：
315419526
负责人：
Professor Dr.-Ing. Markus Bambach
金额：
--
依托单位：
Max-Planck-Institut für Eisenforschung GmbH (MPIE)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/315419526?language=en
关键词：
Consistent physically based modeling dynamic

项目摘要

For the design of hot working processes, a thorough understanding of the evolution of the yield stress and microstructure evolution during dynamic recrystallization (DRX) plays a vital role. In metal forming mainly semi-empirical DRX models are still being used today. These models are not based on internal state variables and are therefore not able to reproduce the physical processes underlying DRX. Thus, an extrapolation beyond the conditions applied in the laboratory during model calibration is inherently fraught with uncertainty. Although physically-based models have the potential to close the existing gaps, significant advancements seem necessary. None of the currently available DRX models takes the current state of metal physics research regarding the initiation and progression of DRX sufficiently into account. Often, it is still assumed that the nucleation of DRX requires a critical dislocation density. Insights into the formation of dislocation density gradients at the grain boundaries, into the formation of cell structures in the grain as a precursor for the formation of mobile sub-grain boundaries, and the interaction of sub-grain boundaries and the high angle grain boundaries of the parent microstructure as nucleation mechanism of DRX have not yet found their way into DRX models. Also, in existing models, the dynamic recovery is not modeled as a function of the stacking fault energy. Even more unsatisfactory is the lack of thermodynamic consistency of existing DRX models. It can be shown that Avrami kinetics (which are often used in DRX models) with an Avrami exponent less than or equal to 3 are inconsistent to the thermodynamically based Poliak-Jonas-criterion for the critical conditions of DRX. However, the usual model assumptions for the nucleation of DRX yield an inconsistent exponent of 3. Both from the viewpoint of metal forming as well as from metal physics, the need for a fundamentally enhanced modeling of DRX arises. The objectives of the present research proposal are therefore, to expand the physical understanding of the initiation and progression of DRX under hot working conditions, to develop a physically-based, stacking-fault-energy-dependent and thermodynamically consistent model for dynamic recrystallization, to prove at the example of a high temperature material (Alloy 800H) that the coupled evolution of the microstructure and yield stress can be described quantitatively correct under hot working conditions by the new model, to implement the model in a finite element software for forming simulation after abolishing the time step dependence of the microstructure evolution as well as to validate the model using a practice-oriented example. With this research existing knowledge gaps in the physically-based modeling of dynamic recrystallization shall be closed and a practice-oriented model for the design of metal forming process shall be created.

对于热加工工艺的设计，充分了解动态再结晶（DRX）过程中的屈服应力和组织演变起着至关重要的作用。在金属成形中，目前仍主要使用半经验DRX模型。这些模型不是基于内部状态变量，因此不能再现DRX下的物理过程。因此，在模型校准期间超出实验室条件的外推法本身就充满了不确定性。虽然基于物理的模型有可能缩小现有的差距，但似乎有必要取得重大进展。目前可用的DRX模型都没有充分考虑关于DRX的启动和进展的金属物理研究的当前状态。通常，仍然假设DRX的成核需要临界位错密度。对晶界处位错密度梯度的形成、作为形成移动的亚晶界的前体的晶粒中的胞状结构的形成以及作为DRX的成核机制的亚晶界和母体微结构的大角度晶界的相互作用的认识尚未进入DRX模型。此外，在现有的模型中，动态恢复没有被建模为堆垛层错能量的函数。更不令人满意的是现有DRX模型缺乏热力学一致性。可以表明，Avrami指数小于或等于3的Avrami动力学（其经常用于DRX模型）与用于DRX的临界条件的基于动力学的Poliak-Jonas准则不一致。然而，通常的模型假设DRX的成核产生不一致的指数为3。无论是从金属成形的观点，以及从金属物理，需要从根本上增强建模的DRX出现。因此，本研究建议的目标是，扩大在热工作条件下的动态再结晶的开始和进展的物理理解，开发一个基于物理的，堆垛层错能量依赖的和物理上一致的动态再结晶模型，以高温材料为例，（800 H合金）的微观组织和屈服应力的耦合演化可以用新模型定量地描述，在消除微观组织演化的时间步长依赖性后，在有限元软件中实现该模型用于成形模拟，并使用面向实践的实例验证该模型。本研究将弥补动态再结晶过程物理模型的不足，为金属成形工艺设计提供一个实用的模型。