Ta-Nb-Hf-Zr-Ti系高熵合金中有序氧复合体的形成和调控机制研究

难熔高熵合金具有高的强度和优异的抗高温软化性能，在航空航天领域具有巨大的应用前景。然而，难熔高熵合金通常具有室温脆性，加工性能不足。针对此问题，本申请拟在Ta-Nb-Hf-Zr-Ti系难熔高熵合金中通过氧掺杂引入有序氧复合体对其进行强韧化。采用实验结合计算模拟对难熔高熵合金氧掺杂前后原子尺度微观结构进行解析，阐明金属组元短程有序促使有序氧复合体形成的物理本质，揭示有序氧复合体的形成机制。进一步，依据平均价电子浓度理论调节Ta-Nb-Hf-Zr-Ti系难熔高熵合金相稳定性，研究其相稳定性对金属组元短程有序及氧掺杂后有序氧复合体形成的影响。同时，研究氧含量对难熔高熵合金中有序氧复合体形成及力学性能的影响。综合难熔高熵合金相稳定性和氧含量的调控，建立基于有序氧复合体强韧化难熔高熵合金的成分设计原则，并将这一强韧化机制应用于钛合金。本项目的完成为利用间隙原子设计高强度高塑韧性金属材料提供理论指导。

Refractory high-entropy alloys (RHEAs) have attracted considerable attention for aerospace applications owing to their unique properties, such as high yield strengths and large softening resistance at elevated temperatures. However, RHEAs are normally brittle at room temperature, resulting in insufficient processing capability. To address this challenge, this project will introduce ordered oxygen complexes (OOCs) into Ta-Nb-Hf-Zr-Ti RHEAs via alloying oxygen and investigate the toughening mechanism. Firstly, the atomic-scale microstructure of RHEAs before and after doping oxygen will be deciphered through experimental and computational investigations. On basis of this, the physical essence of short-range orders of metallic elements promoting the formation of OOCs will be expounded, and then the formation mechanism of OOCs will be disclosed. Secondly, based on the average valence electron concentration theory, the phase stability of Ta-Nb-Hf-Zr-Ti RHEAs will be tuned, and then the effects of phase stability on the short-range orders of metallic elements and the formation of OOCs after doping oxygen will be explored. Also, the effects of oxygen contents on the formation of OOCs and the corresponding mechanical properties of RHEAs will be studied. Finally, via tuning the phase stability and oxygen contents of RHEAs, a universal alloy design criterion based on OOCs for strengthening and toughening RHEAs will be established, and the OOC-mediated strain hardening mechanism will be extended to titanium alloys. The implement of the proposed research will provide theoretical guidance for designing advanced metallic materials with high strength and ductility via doping interstitial atoms.