Deformation Behavior and Strengthening Mechanisms of an Additively Manufactured High-Entropy Alloy with Hierarchical Heterostructures

Additive manufacturing (AM) of high-entropy alloys (HEAs) typically results in the formation of unique microstructures and deformation mechanisms, sparking widespread research interest. This study delves into the deformation behavior and strengthening mechanisms of an AMed HEA with hierarchical heterostructures. The results show that the alloy consists of the FCC matrix, coherent L12 precipitates, incoherent L21 precipitates with lens-shaped inclusions, and chemical cells. The distribution of the L21 phase and the lens-shaped inclusions are unique phenomena, mainly attributed to local chemical fluctuations during the AM process. The FCC matrix primarily contributes to plastic deformation, with L12 precipitates enhancing strength through ordered strengthening, and L21 precipitates providing strengthening via Orowan bypassing mechanism. Additionally, dislocation strengthening also contributes to the overall strength. Notably, the lensshaped structures within the L21 phase undergo a stress-induced martensitic transformation during deformation, attributed to their inherent metastability, favorable microstructural locations and grain orientations. These findings deepen the understanding of the microstructures and deformation mechanisms of AMed HEAs, offering valuable insights for the design and optimization of high-performance HEAs in the future.