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?

该项目的目的仍在继续增加可能的形成速度，同时通过使用等量通道的角压（ECAP），同时降低铝板超塑形形成（SPF）的温度。对于两个项目合作伙伴，还会出现其他新问题和工作包。形成技术（UTG）：研究项目的结果表明，现有的ECAP工具可以形成铝纸材料。但是，样品厚度和通道几何形状之间的性能在钣金的ECAP中比常规ECAP中的剪切变形较低。如果更改通道的几何形状以促进该比率并减少通道半径，则板厚厚度的明显无限性以及内角半径出现的裂纹。这些问题应通过应用反压来减少。在数值研究的基础上，可以证实该措施对材料材料有效。通过实施反击，可以采取实验室方法ECAP的工业应用迈出的重要一步。因此，列出的问题是从生产工程的角度出现的：•如何在Ecap-tool中实现板材材料中的反压力，以进一步增加引入的剪切菌株？•如何选择这种相应的频道配置，以实现无裂纹表面并在材料中获得最均匀的应变分布？材料科学（LWW）：在项目的范围内，已经显示了对ECA加工金属对所达到菌株的热处理的明显影响。这是由于形成的微观结构的热稳定性。借助特定的恢复或重结晶热处理，可以调整具有不同热稳定性的微观结构，并可以研究其对超塑性形成过程的适用性。因此，重点是在不同的摄入后热处理后塑性变形过程中对微观结构机制的基本了解。通过（传播）电子显微镜方法对不同的微观结构进行调整，随后在不同温度下进行变形行为，应在拉伸测试中表征应变速率。从物质科学的角度来看，出现了以下问题，其答案将对项目的整体成功产生重大贡献：•热处理期间哪些微观结构过程会影响成就（Super）塑性应变？•UFG微结构的热稳定性有什么影响，而动态恢复值在何种程度上会在热形成过程中改变应变值？