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Microstructure and strengthening mechanisms of carbon doping and Al2O3 addition refractory high-entropy alloy composites
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Y
张
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DOI：10.1007/s42243-026-01882-5.png)
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Abstract
En 中文
Refractory high-entropy alloys (RHEAs) for extreme service environments require targeted mechanical property optimization. For this purpose, four NbMoTaWV-based RHEA/ceramic composites (undoped N, C-doped NC, 1 wt.% Al2O3-reinforced NCA-1, 5 wt.% Al2O3-reinforced NCA-5) were fabricated via mechanical alloying combined with rapid vacuum hot pressing. The effects of carbon doping and Al2O3 addition on phase composition, microstructure, and hardness were systematically investigated via multi-scale characterization and hardness testing, focusing on the synergy of multiple strengthening mechanisms. Results show that all samples possess ultrafine-grained structures in the nano- to submicron-scale. Carbon doping forms high-hardness W2C and Mo2C carbides, introducing significant precipitation strengthening. 1 wt.% Al2O3 refines and homogenizes grains, promotes the formation of a single (Ta,V)2O5 high-entropy ceramic phase, and achieves highly efficient strengthening synergy. Excessive Al2O3 causes local grain coarsening, breaking the synergistic balance and weakening the strengthening effect. Multi-scale hardness tests confirm the base N sample reaches 1473.19 HV; the NC sample achieves a 5.83% hardness increase; the optimal NCA-1 sample obtains a nearly 10% hardness improvement with a peak nanohardness of 24.558 GPa. The composition–microstructure–property correlation of the four RHEAs was revealed, and the addition of 1 wt.% Al2O3 was identified as the optimal parameter, and a reasonable design guidance for high-performance RHEA fabrication was introduced.
Keywords:
Refractory high-entropy alloy
Carbon doping
Al2O3
Microstructure
Strengthening mechanism
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