Improvement of the high strain rate superplasticity of aluminum materials by equal channel angular pressing of sheet metals

板材等通道角冲压改善铝材高应变率超塑性

• 批准号: 376797652
• 负责人: Professor Dr.-Ing. Wolfram Volk
• 金额: --
• 依托单位: Lehrstuhl für Umformtechnik und Gießereiwesen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/376797652?language=en
• 关键词: Improvement; strain; rate; superplasticity; aluminum

The aim of this project continuation is still to increase the possible forming speed while simultaneously reducing the temperature for superplastic forming (SPF) of aluminum sheets by using Equal-channel Angular Pressing (ECAP). For both project partners, additional new questions and work packages arise. Forming technology (utg):The results of the research project have shown that forming of aluminium sheet materials is possible with the existing ECAP tool. However, the proportions between sample thickness and channel geometry cause lower shear deformations in the ECAP of sheet metal than in conventional ECAP. If the channel geometry is changed in favour of this ratio and the channel radii are reduced, significant inhomogeneities over the sheet thickness and cracks at the inner corner radius occur. These problems should be reduced by applying a counterpressure. On the basis of numerical investigations, this measure can already be confirmed as effective for sheet materials. By implementing a counterpressure, a significant step towards the industrial applicability of the laboratory method ECAP can be taken. The listed questions consequently arise from a production engineering perspective:• How is a counterpressure implemented in the ECAP-tool for sheet materials in order to further increase the shear strains introduced?• How must this counterpressure and the corresponding channel configuration be selected in order to achieve a crack-free surface and a most homogeneous strain distribution in the sheet material? Materials Science (LWW):Within the scope of the project, a pronounced influence of a heat treatment of the ECA-processed sheet metal on the achievable strains has been shown. This is due to the thermal stability of the formed microstructure. With the help of specific recovery or recrystallisation heat treatments, microstructures with different thermal stability can be adjusted and their suitability for superplastic forming processes can be investigated. The focus is therefore on obtaining a fundamental understanding of the microstructural mechanisms during plastic deformation after different post-ECAP heat treatments. Different microstructures will be adjusted, examined by (transmission) electron microscopic methods and subsequently their deformation behaviour at different temperatures and strain rates will be characterised in tensile tests. From a materials science point of view, the following questions arise, the answers to which will contribute significantly to the overall success of the project: • Which microstructural processes during post heat treatment influence the achievable (super)plastic strain?• What influence does the thermal stability of the UFG microstructure have and to what extent does dynamic recrystallization change the strain values during hot forming?

本项目延续的目的仍然是提高可能的成形速度，同时降低使用双通道角挤压（ECAP）的铝板超塑性成形（SPF）的温度。对于两个项目合作伙伴来说，会出现额外的新问题和工作包。成形技术（utg）：研究项目的结果表明，使用现有的ECAP工具可以成形铝板材料。然而，样品厚度和通道几何形状之间的比例导致较低的剪切变形在ECAP的金属板材比在传统的ECAP。如果通道的几何形状改变有利于这个比例和通道半径减小，显着的不均匀性超过板厚度和裂纹的内角半径发生。这些问题应该通过施加反压力来减少。在数值研究的基础上，这种措施已经可以被证实是有效的板材。通过实施反压力，可以向实验室方法ECAP的工业适用性迈出重要的一步。因此，从生产工程的角度来看，会出现以下问题：· 如何在ECAP工具中对板材实施反压力，以进一步增加引入的剪切应变？· 为了在板材中实现无裂纹表面和最均匀的应变分布，必须如何选择这种反压力和相应的通道结构？材料科学（LWW）：在该项目的范围内，已经显示出对ECA加工的金属板进行热处理对可实现的应变的显著影响。这是由于所形成的微结构的热稳定性。借助特定的回复或再结晶热处理，可以调整具有不同热稳定性的微观结构，并研究其对超塑性成形工艺的适用性。因此，重点是在不同的后ECAP热处理后的塑性变形过程中获得的微观组织机制的基本理解。将调整不同的微观结构，通过（透射）电子显微镜方法进行检查，随后将在拉伸试验中表征它们在不同温度和应变速率下的变形行为。从材料科学的角度来看，会出现以下问题，这些问题的答案将大大有助于项目的整体成功：· 后热处理过程中的哪些微观组织过程会影响可实现的（超）塑性应变？· UFG显微组织的热稳定性有什么影响？动态再结晶在多大程度上改变了热成形过程中的应变值？