The refinement and thermal stability of intermediate theta-prime (${\theta }^{\prime }$) 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 ${\theta }^{\prime }$ precipitates. The formation of Al₃(Sc, Zr) core/shell dispersoids significantly refine the ${\theta }^{\prime }$ 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 ${\theta }^{\prime }$ precipitates, and greatly slows the growth and coarsening of the ${\theta }^{\prime }$ precipitates at elevated temperatures. Differential scanning calorimetry (DSC) shows that this can be attributed to an enhanced nucleation and improved coarsening resistance of the ${\theta }^{\prime }$ 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 ${\theta }^{\prime }$ 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 ${\theta }^{\prime }$ precipitates, Mn not only refines the ${\theta }^{\prime }$ precipitates, but also greatly enhances their coarsening resistance and corresponding alloy's thermal stability.

中间theta-prime（${\theta }^{\prime }$）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。${\theta }^{\prime }$沉淀。Al ₃（Sc，Zr）核/壳弥散体的形成显着改善了${\theta }^{\prime }$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。${\theta }^{\prime }$ 沉淀，大大减慢了合金的生长和粗化 ${\theta }^{\prime }$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。${\theta }^{\prime }$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。${\theta }^{\prime }$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。${\theta }^{\prime }$ 沉淀，Mn不仅可以提炼 ${\theta }^{\prime }$ 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。