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Improvement of formability of extruded aluminium profiles by a local short-term heat treatment

通过局部短期热处理改善挤压铝型材的成形性

基本信息

批准号：
246974870
负责人：
Professor Dr.-Ing. Olaf Keßler
金额：
--
依托单位：
Lehrstuhl für Fertigungstechnologie (LFT)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/246974870?language=en
关键词：
Improvement formability extruded aluminium profiles

项目摘要

The objective of the research project is the improvement of forming limits and the defined adjustment of final mechanical properties of bended aluminium extrusion profiles by a tailored local short-term heat treatment before forming, resulting in so called Tailor Heat Treated Profiles (THTP). In the first project period THTP of aluminium alloy 6060 T4 have been investigated.Microstructure changes due to short-term retrogression annealing have been in-situ characterised by differential scanning calorimetry (DSC) and a newly developed method for investigation of a wide range of heating rates. Mechanical properties after short-term heat treatment have been described depending on heating method and subsequent ageing processes. Microstructure changes have been correlated with mechanical properties and displayed in a continuous heating dissolution diagram of 6060 T4 including a suitable process window. For the forming simulation as well as for the heat treatment simulation of THTP, models have been implemented by LS-DYNA, which in future can be coupled into an integrated process model. A test rig for bending including an in-situ deformation measurement has been implemented and extrusion profiles have been successfully bended and characterized in comparison with the numerical results.Based on the results of the first project period new thematic fields have been developed, which shall be researched for a significant improvement of THTP. Thus, the focus of the second project period lies on the one hand on the enhancement of the fundamental understanding of cause-effect relationships regarding short- term heat treatment, microstructure changes and resulting mechanical properties. On the other hand, the accuracy of the numerical calculation shall be improved by more complex material models and a precise description of the thermo-mechanical processes during short-term heat treatment. Therefore, anisotropic properties of aluminium extrusion profiles must be considered. Further, the locally different cooling rates after short-term retrogression annealing play an important role. The high alloyed and high-strength aluminium alloy 6082 T4 with a different dissolution and precipitation behaviour shall be incorporated into the investigations. In addition, temperature gradients along profile wall thickness as well as residual stresses from the short-term heat treatment shall be considered in numerical calculation steps. Finally, a stabilization treatment after short-term heat treatment shall be introduced to preserve the artificial ageing potential.

该研究项目的目标是通过在成形前进行量身定制的局部短时热处理来提高弯曲铝型材的成形极限并明确调整最终的力学性能，从而产生所谓的裁剪热处理型材(THTP)。在第一个项目阶段，对6060T4铝合金的THTP进行了研究。利用差示扫描量热仪(DSC)和一种新开发的宽升温范围的研究方法，原位表征了短期回归退火引起的组织变化。对短期热处理后的机械性能进行了描述，这取决于加热方法和随后的老化过程。显微组织的变化与力学性能相关，并显示在6060T4的连续加热溶解图中，该图包括一个合适的工艺窗口。对于THTP的成形模拟和热处理模拟，已经用LS-DYNA实现了模型，将来可以耦合到一个完整的工艺模型中。建立了包括现场变形测量在内的弯曲试验台，成功地弯曲了挤压型材，并与数值结果进行了比较。在第一个项目阶段的结果的基础上，开发了新的主题领域，这些领域将为THTP的显著改进而研究。因此，第二个项目期的重点一方面在于加强对短期热处理、组织变化和由此产生的机械性能的因果关系的基本了解。另一方面，通过更复杂的材料模型和对短期热处理过程的热机械过程的精确描述，可以提高数值计算的精度。因此，必须考虑铝型材的各向异性。此外，短期退火后局部不同的冷却速度也起到了重要作用。具有不同溶解和析出行为的高合金化和高强度铝合金6082 T4应纳入研究范围。此外，在数值计算步骤中，还应考虑型材壁厚方向的温度梯度以及短期热处理产生的残余应力。最后，应在短期热处理后进行稳定化处理，以保持人工老化潜力。