Additive manufacturing provides an efficient way of producing metallic components with complex geometries. Their microstructure is substantially different to those from conventional processing, creating opportunities for manipulating the final microstructure and properties via heat treatment. Here, we demonstrate that as-built heterostructures in an Al-Zn-Mg-Cu-Nb alloy produced during the solidification of molten pools provide a driving force and additional Zener pinning sources for recrystallization. This creates a bimodal grain structure after solution treatment, causing additional hetero-deformation-induced strengthening and hardening. Coarse grains are found to promote work hardening and blunt the propagate of cracks during deformation, increasing ductility. Together with precipitation strengthening from a high number density nanoprecipitates, the simultaneous improvement of strength and ductility in a highly alloyed Al-Zn-Mg-Cu-Nb alloy is achieved. These results provide a simple strategy for the development of additively manufactured age-hardening alloys with improved strength and ductility for high performance structural applications.

增材制造提供了一种生产具有复杂几何形状的金属部件的有效方法。它们的微观结构与传统加工的微观结构有很大不同，为通过热处理控制最终的微观结构和性能创造了机会。在这里，我们证明了在熔池凝固过程中产生的 Al-Zn-Mg-Cu-Nb 合金中的竣工异质结构为再结晶提供了驱动力和额外的齐纳钉扎源。这会在固溶处理后产生双峰晶粒结构，从而引起额外的异质变形诱导的强化和硬化。研究发现，粗晶粒可促进加工硬化并减缓变形过程中裂纹的传播，从而提高延展性。与高数密度纳米沉淀物的沉淀强化一起，实现了高合金 Al-Zn-Mg-Cu-Nb 合金的强度和延展性的同时提高。这些结果为开发增材制造的时效硬化合金提供了一个简单的策略，该合金具有更高的强度和延展性，适用于高性能结构应用。