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Coupled segregation mechanisms of Sc, Zr and Mn at θ′ interfaces enhances the strength and thermal stability of Al-Cu alloys
Acta Materialia ( IF 8.3 ) Pub Date : 2021-01-08 , DOI: 10.1016/j.actamat.2021.116634
Lu Jiang , Baptiste Rouxel , Timothy Langan , Thomas Dorin

The refinement and thermal stability of intermediate theta-prime (θ) precipitates are critical in the development of new high strength 2xxx series aluminium-copper (Al-Cu) alloys for high temperature applications. In this work, we use trace additions of Sc, Zr and Mn in an Al-6.5 wt.% Cu alloy to refine and stabilise the θ precipitates. The formation of Al3(Sc, Zr) core/shell dispersoids significantly refine the θ precipitates by acting as preferential nucleation sites during artificial ageing. Adding Mn results in a significant increase of hardness during ageing at 190 °C. Hardness is maintained during thermal exposure at 280 °C for up to 24 h. Transmission electron microscopy (TEM) reveals that the addition of Mn leads to a finer and denser distribution of θ precipitates, and greatly slows the growth and coarsening of the θ precipitates at elevated temperatures. Differential scanning calorimetry (DSC) shows that this can be attributed to an enhanced nucleation and improved coarsening resistance of the θ precipitates in the presence of Mn. Atom probe tomography (APT) reveals that the enhanced age-hardening kinetics and thermal stability arise from the independent segregation mechanisms of Mn, Sc and Zr at the semi-coherent and coherent interfaces of the θ precipitates. The segregation is quantified by calculating the Gibbsian interfacial excess and corresponding reduction in interfacial energy. These calculations reveal that while Sc and Zr play a significant role in the refinement of the θ precipitates, Mn not only refines the θ precipitates, but also greatly enhances their coarsening resistance and corresponding alloy's thermal stability.



中文翻译:

Sc,Zr和Mn的耦合偏析机理 θ 界面增强了Al-Cu合金的强度和热稳定性

中间theta-prime(θ)沉淀对于开发用于高温应用的新型高强度2xxx系列铝铜(Al-Cu)合金至关重要。在这项工作中,我们在Al-6.5 wt%的Cu合金中使用痕量的Sc,Zr和Mn来精炼和稳定合金。θ沉淀。Al 3(Sc,Zr)核/壳弥散体的形成显着改善了θ通过在人工时效过程中充当优先成核位点而沉淀出来。添加Mn会导致190°C时效时硬度显着增加。在280°C的温度下暴露长达24小时,可以保持硬度。透射电子显微镜(TEM)显示,Mn的添加会导致Mn的分布更细密。θ 沉淀,大大减慢了合金的生长和粗化 θ在高温下沉淀。差示扫描量热法(DSC)表明,这可以归因于增强的成核作用和改善的耐粗化性。θ在Mn存在下沉淀。原子探针层析成像(APT)表明,增强的时效硬化动力学和热稳定性来自Mn,Sc和Zr在合金半相干和相干界面处的独立偏析机理。θ沉淀。通过计算吉布斯界面过量和界面能的相应减少来量化偏析。这些计算表明,尽管Sc和Zr在精炼合金中起着重要作用。θ 沉淀,Mn不仅可以提炼 θ 沉淀,但也大大提高了它们的耐粗化性和相应合金的热稳定性。

更新日期:2021-01-18
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