Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW-6060 T4 extrusion profiles: Part A
Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW-6060 T4 extrusion profiles: Part A
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DOI：
10.1007/s11740-016-0683-6
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发表时间：
2016-10-01
影响因子：
1.7
通讯作者：
Kessler, Olaf
中科院分区：
文献类型：
--
作者：
Froeck, Hannes;Graser, Matthias;Kessler, Olaf
铝合金应用于各个工业领域，在减轻重量方面发挥着重要作用，特别是在汽车工业中。由于其较高的强度，时效硬化合金通常是首选。然而，与低碳钢等其他材料相比，冷成形性相当低，因此，复杂的零件在较高的温度下几乎无法生产。提高铝合金冷成形性的一种可能是所谓的定制热处理。在这种方法中，进行短期热处理以实现材料的局部软化，这是由于强化团簇的溶解（倒退）。利用这种效应改善了材料流动，缓解了临界成形区，提高了材料的整体成形性。之后，强度可以通过老化再次增加。然而，到目前为止，定制热处理主要用于铝板。此外，考虑到所有工艺参数以及微观结构发现的完整集成的整体工艺理解是缺失的。因此，研究了EN AW-6060 T4铝合金定制热处理型材（THTP）在加热过程中的溶解和析出行为。用差示扫描量热法（DSC）记录了从20到600℃的加热曲线，加热速率为0.01至5 K/s。根据一条dsc曲线的峰值温度，进行了类似热处理后的拉伸试验。结果表明，拉伸试验获得的力学性能与DSC测量的显微组织结果相一致。微观结构和力学性能的相关性使得通过局部软化来开发THTP的最佳参数得以推导。第二部分讨论了后续成形工艺的热处理参数以及不同短期热处理后自然时效过程中力学性能的变化。
Aluminium alloys are applied in various industrial fields and play an important role concerning weight reduction especially in the automotive industry. Because of their higher strength, age-hardening alloys are commonly preferred. However, the cold formability in comparison to other materials like mild steels is quite low and due to this, complex parts are hardly producible at higher temperatures. One possibility to improve the cold formability of aluminium alloys is the so called tailor heat treatment. In this approach, a short-term heat treatment is conducted to achieve a local softening of the material due to dissolution of strengthening 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 aging. However, up till now tailor heat treatment has mainly been used for aluminium sheet. Further, a holistic process understanding, taking into account all process parameters as well as a complete integration of microstructural findings is missing. Therefore, the dissolution and precipitation behaviour during heating of Tailor Heat Treated Profiles (THTP) from the aluminium alloy EN AW-6060 T4 is investigated. Heating curves from 20 to 600 A degrees C with heating rates of 0.01 up to 5 K/s are recorded, using the differential scanning calorimetry (DSC). Based on the peak temperatures of one DSC-curve, tensile tests were carried out after a comparable heat treatment. It is shown, that the mechanical properties gained by the tensile test correlate with the microstructure results of the DSC measurements. The correlation of the microstructure and the mechanical properties enables the derivation of optimal parameters for the development of THTP through a local softening. In Part B the heat treatment parameter for the subsequent forming process as well as the evolution of the mechanical properties during natural aging after different short-term heat treatments are discussed.