Exceptional High‐Temperature Strength of a Lightweight MoNbTiV x ZrSi Refractory High‐Entropy Alloys Strengthened by a Stable Hyper‐Eutectic Microstructure

A novel series of MoNbTiV x ZrSi ( x = 0.25, 1.0) lightweight refractory high‐entropy alloys (RHEAs) was designed by tuning V content. Phase formation was predicted using key thermodynamic parameters (Δ H mix , Δ S mix , δ , VEC), and correlated with microstructure and mechanical properties. The results indicate that both alloys exhibit a hyper‐eutectic structure, consisting of primary M 5 Si 3 and a (body‐centered cubic (BCC) + M 5 Si 3 ) eutectic structure. With increasing V from 0.25 to 1.0, the BCC phase fraction increases from 43.36% to 48.91%, simultaneously refining M 5 Si 3 morphology and eutectic spacing. Performance tests indicate that this alloy system exhibits exceptional strength at both room and elevated temperatures. At room temperature, the alloy achieves hardness as high as 812.8 and 745.1 HV, significantly surpassing those of most reported RHEAs. Compression tests reveal that the R0.25 and R1.0 alloys exhibit high room‐temperature yield strengths of 1583 and 1667 MPa, respectively, while achieving fracture strains of 14.2% and 20.8%. At 873 K, these alloys maintain excellent strength, with yield strengths reaching 1392 and 1552 MPa, demonstrating significant potential for high‐temperature applications. The fine eutectic structure not only enhances the alloy's performance, enabling it to outperform similar dual‐phase systems, but also provides valuable insights for designing silicide‐reinforced RHEAs with outstanding properties.