Quantitative analysis of local deformation and direct correlation with microstructural and mechanical parameters during equal channel angular pressing in tools with variable geometries

可变几何形状工具等通道角冲压过程中局部变形的定量分析以及与微观结构和机械参数的直接相关性

• 批准号: 465563128
• 负责人: Professor Dr.-Ing. Martin Franz-Xaver Wagner
• 金额: --
• 依托单位: Professur Werkstoffwissenschaft
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465563128?language=en
• 关键词: Quantitative; analysis; local; deformation; direct

Equal Channel Angular Pressing (ECAP) is a processing technique that allows to subject metallic materials to severe plastic deformation which leads to massive grain refinement. The resulting ultrafine-grained materials are characterized by exceptional mechanical properties (high strength in combination with good ductility), making them potentially attractive for applications in, for instance, light-weight design. While the effect of ECAP on microstructure and properties of many alloys has been studied in great detail in recent years, there still exists a fundamental knowledge gap with respect to local deformation in the plastic deformation region of different ECAP tools: typically, equivalent strains are only estimated based on simplified models that do not consider, for example, the experimentally documented effects of material hardening or of a commonly applied back-pressure. A more detailed understanding of local (plastic) deformation, however, is needed in order to quantitatively describe the interrelationships between microstructural deformation mechanisms and grain refinement, which have only been analyzed qualitatively so far, and to fundamentally study and predict physical metallurgy processes as a function of material and processing parameters. The principal investigator has recently extended an analytical model that accurately describes the local deformation in 90°-ECAP tools along flow lines such that it can be also used to analyze arbitrary tool geometries. In combination with a high-resolution visioplastic technique, also developed in preliminary work, there now exists a tool-set that allows to study the key hypothesis of this proposal – the assumption that the actual equivalent strain (as expressed by the flow line exponent, its gradient in the work-piece, and the evolution of these parameters with increasing number of ECAP passes) represents a physically relevant measure that can be corelated with (or even used to quantitatively predict) many different phenomena, like microstructural and texture evolution, material properties, or damage accumulation. In this project, three model alloys and four different ECAP tools will be used to experimentally characterize the plastic deformation region under different processing conditions and how plastic deformation proceeds along different flow lines. Image recognition algorithms, based on artificial intelligence, will be developed and used to accurately fit local deformation on three complementary levels. This will for the first time also allow to evaluate the quality of different flow line models and thus to provide a benchmark test for different modeling approaches that are currently established in the ECAP community. Finally, the experimental and theoretical work will also provide the means to clearly identify relevant processing and material parameters, and to directly relate them with the resulting macroscopic properties.

等通道转角挤压（ECAP）是一种允许金属材料经受剧烈塑性变形从而导致大量晶粒细化的加工技术。由此产生的超细晶粒材料的特征在于优异的机械性能（高强度与良好的延展性相结合），使它们在例如轻量化设计中的应用中具有潜在的吸引力。虽然近年来已经非常详细地研究了ECAP对许多合金的微观结构和性能的影响，但是对于不同ECAP工具的塑性变形区域中的局部变形仍然存在基本的知识差距：典型地，等效应变仅基于不考虑，例如，材料硬化或通常施加的背压的实验记录的效果。然而，需要对局部（塑性）变形有更详细的了解，以便定量地描述微观结构变形机制和晶粒细化之间的相互关系，到目前为止，这只是定性地分析，并从根本上研究和预测物理冶金过程作为材料和工艺参数的函数。主要研究者最近扩展了一个分析模型，精确地描述了局部变形，在90°-ECAP工具沿着流线，使它也可以用来分析任意的工具几何形状。结合在前期工作中开发的高分辨率电塑性技术，现在存在一套工具，可以研究该提案的关键假设-假设实际等效应变（由流线指数表示，其在工件中的梯度，这些参数随着ECAP道次的增加而变化）代表了一种物理相关的测量，（或甚至用于定量预测）许多不同的现象，如微观结构和织构演化、材料特性或损伤累积。在这个项目中，三种模型合金和四种不同的ECAP工具将被用来实验表征在不同的加工条件下的塑性变形区域，以及塑性变形如何沿着不同的流线进行。将开发和使用基于人工智能的图像识别算法，以便在三个互补水平上准确地拟合局部变形。这也将首次允许评估不同流线模型的质量，从而为ECAP社区目前建立的不同建模方法提供基准测试。最后，实验和理论工作还将提供明确识别相关工艺和材料参数的方法，并将其与所得宏观性能直接联系起来。