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Micro residual stresses in hard metals

硬质金属中的微小残余应力

基本信息

批准号：
313772342
负责人：
Professor Dr.-Ing. Christoph Broeckmann
金额：
--
依托单位：
Institut für Anwendungstechnik Pulvermetallurgie und Keramik (IAPK)
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 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/313772342?language=en
关键词：
Micro residual stresses hard metals

项目摘要

Using the example of tungsten carbide cobalt hardmetals a finite element model is developed which enables the precise prediction of type II residual stresses in liquid phase sintered, heterogeneous metal matrix composites. Based on a temperature dependent, crystal-(visco)-plastic constitutive description of the cobalt binder, an orthotropic thermo-elastic constitutive formulation of the tungsten carbide and the consideration of the influence of volume changes on the type II residual stress response, caused by precipitation of tungsten carbide the following objectives are pursued: 1. The accurate and precise prediction of the residual stresses and the development of the internal stresses depending on the cooling history and the microstructural features of the hardmetal. 2. The qualitative investigation of the influence of precipitation of tungsten carbide out of the binder during the cooling from sintering temperature. 3. The statistical validation of the simulation results based on the investigation of multiple 3D models based on electron backscatter diffraction data (EBSD) and focused ion beam (FIB) techniques. 4. Verification of the simulated results by residual stress measurements performed on hard metals with varying processing history. 5. Identification of a combination of microstructural features and cooling cycle which leads to a minimal residual stress state. For achieving the above mentioned targets the constitutive laws are implemented into the l finite element software Abaqus by the use of different user defined subroutines. The parameters for the crystal-(visco)-plastic model are derives form temperature dependent mechanical experiments on single crystals made of a representative cobalt binder alloy. Finite element models are automatically derived from EBSD data by a self-developed software which detects the crystal orientation and cobalt-/-carbide boundaries. By performing multiple simulations, which are based on realistic processing parameters, the residual stress distribution within the microstructure is predicted and information for the optimization of the manufacturing process can be derived. The simulation results are verified by measuring the residual stresses in hard metals with varying processing history using X-Ray and neutron diffraction techniques. Besides a more accurate prediction of the residual stress state in tungsten carbide materials, the model will lead to a better understanding of the mechanisms causing residual stresses in these materials.

以碳化钨钴硬质合金为例，建立了能够精确预测液相烧结非均相金属基复合材料II型残余应力的有限元模型。基于温度依赖性、钴粘结剂的结晶（粘）塑性本构描述、碳化钨的正交各向异性热弹性本构公式以及考虑体积变化对碳化钨析出引起的II型残余应力响应的影响，本文追求以下目标：1。根据冷却过程和硬质合金的显微组织特征，准确准确地预测残余应力和内应力的发展。2. 从烧结温度出发，定性研究了冷却过程中碳化钨析出粘结剂的影响。3. 基于电子后向散射衍射（EBSD）和聚焦离子束（FIB）技术对多个三维模型的仿真结果进行了统计验证。4. 通过对不同加工历史的硬质金属进行残余应力测量来验证模拟结果。5. 识别导致最小残余应力状态的显微组织特征和冷却循环的组合。为了实现上述目标，本构律通过使用不同的用户自定义子程序实现到有限元软件Abaqus中。晶体（粘）塑性模型的参数是由具有代表性的钴结合剂合金单晶的温度相关力学实验得出的。通过自行开发的软件自动从EBSD数据中导出有限元模型，该软件可以检测晶体取向和钴/碳化物边界。通过基于实际加工参数的多次模拟，预测了微观组织内的残余应力分布，为优化制造工艺提供了信息。利用x射线和中子衍射技术测量不同加工历史的硬质金属的残余应力，验证了模拟结果。除了能更准确地预测碳化钨材料的残余应力状态外，该模型还将有助于更好地理解这些材料中残余应力的产生机制。