Stabilization of 7xxx aluminium alloys
Stabilization of 7xxx aluminium alloys
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DOI：
10.1016/j.jallcom.2018.01.003
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发表时间：
2018-04
影响因子：
6.2
通讯作者：
J. Österreicher;G. Kirov;S. Gerstl;Ermal Mukeli;F. Grabner;Manoj Kumar
中科院分区：
文献类型：
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作者：
J. Österreicher;G. Kirov;S. Gerstl;Ermal Mukeli;F. Grabner;Manoj Kumar
高强度Al-Zn-Mg（-Cu）合金很少用于汽车工业，这是由于淬火后明显的自然时效和导致的室温下差的可成形性。此外，烤漆响应通常是次优的。为了克服这些挑战，我们进行了各种低温预老化处理，然后在室温下储存，并进行了模拟工业油漆烘烤的短暂高温热处理。的中间和最终的机械性能进行了评估和纳米结构，沉淀和局部化学的样品进行了研究，通过原子探针断层扫描和差示扫描量热法。结果发现，适当设计的稳定化处理可以抑制AA 7021中的自然老化过程，从而导致稳定状态，其硬度低于自然老化超过约一周的样品。原子探针断层扫描显示，稳定化导致Mg和Zn的共沉淀（指示GP区），阻碍了在三周的过程中硬度的进一步增加。此外，AA 7075的烤漆响应得到改善，导致屈服强度仅比峰值老化样品低2%。
High strength Al-Zn-Mg(-Cu) alloys are rarely used in the automotive industry due to pronounced natural ageing after quenching and resulting poor formability at room temperature. Furthermore, the paint bake response is often suboptimal. To overcome these challenges, we performed various low temperature pre-ageing treatments followed by storage at room temperature and a short high temperature heat treatment simulating industrial paint baking. The intermediate and final mechanical properties were assessed and the nanostructure, precipitation, and local chemistries of the samples were studied by atom probe tomography and differential scanning calorimetry. It was found that a properly designed stabilization treatment can inhibit the natural ageing process in AA7021 resulting in a stable condition with a lower hardness than samples naturally aged for longer than approximately one week. Atom probe tomography revealed that the stabilization leads to co-precipitation of Mg and Zn (indicating GP-zones) hindering the further increase in hardness over the course of three weeks. Furthermore, the paint bake response of AA7075 was improved resulting in yield strength only 2% short of a peak aged sample.