Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW-6060 T4 extrusion profiles-Part B
Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW-6060 T4 extrusion profiles-Part B
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DOI：
10.1007/s11740-016-0684-5
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发表时间：
2016-10-01
影响因子：
1.7
通讯作者：
Merklein, Marion
中科院分区：
文献类型：
--
作者：
Graser, Matthias;Froeck, Hannes;Merklein, Marion
在汽车工业中，铝及其相应的半成品为车身结构的减重目标做出了重要贡献。具有Mg和Si含量的6000系列铝合金是优选的，因为通过时效处理可以增加强度。然而，与低碳钢等其他材料相比，冷成形性相当低，因此，复杂的零件只能在较高的温度下生产。因此，开发了所谓的Tailor热处理以改善铝合金的冷成形性。在这种方法中，进行短期热处理以实现由于Mg和Si团簇的溶解（退化）而导致的材料的局部软化。这种效应用于改善材料流动，缓解关键成形区域并提高材料的整体成形性。之后，强度可以通过老化过程再次增加。然而，到目前为止，一个整体的过程理解，考虑到所有的过程参数以及微观结构的解释是失踪。因此，基础研究的重点在于机械性能和短期热处理与工业相关的加热速率以及自然和人工时效过程之间的联系。最后，将自然老化过程中力学性能的演变与A部分中讨论的DSC分析结果进行了比较。基于这些结果，一个工艺窗口，推导出后续的成型工艺和最终的机械性能的最终部件的成型历史以及人工时效工艺的依赖，被确定。
In the automotive industry aluminium and its corresponding semi-finished products contribute an essential part to the aim of weight reduction in car body structures. Aluminium alloys of the 6000 series with Mg and Si contents are preferred because of the possibility to increase strength by ageing processes. However, the cold formability in comparison to other materials like mild steels is quite low and due to this, complex parts are only producible at higher temperatures. Therefore, the so called Tailor Heat Treatment was developed to improve the cold formability of aluminium alloys. In this approach, a short-term heat treatment is conducted to achieve a local softening of the material due to dissolution of Mg and Si clusters (retrogression). This effect is used to improve the material flow, relief critical forming zones and enhance the overall formability of the material. Afterwards, strength can be increased again by ageing processes. However, up till now a holistic process understanding, taking into account all process parameters as well as a microstructural explanation is missing. Therefore, the focus of the fundamental investigations lies on connections between the mechanical properties and short-term heat treatment with industry-relevant heating rates as well as natural and artificial ageing process. Conclusively, the evolution of the mechanical properties with regard to the natural ageing process is compared with findings of DSC analysis, which were discussed in Part A. Based on these results, a process window is derived for the subsequent forming process and the final mechanical properties of the final part in dependency of the forming history as well as the artificial ageing process, are identified.