Enhancement of comprehensive properties of Nb–Si based in-situ composites by Ho rare earth doping

• Published in: Rare metals 2024-09, Vol.43 (9), p.4508-4520
• Main Authors: Wei, Wei, Wang, Qi, Chen, Rui-Run, Zheng, Chao-Wen, Su, Yan-Qing
• Format: Article
• Language: English
• Subjects: Alloys; Biomaterials; Chemistry and Materials Science; Doping; Energy; Eutectic alloys; Materials Engineering; Materials Science; Mechanical properties; Metallic Materials; Molecular composites; Nanoscale Science and Technology; Original Article; Oxidation; Oxidation resistance; Oxygen; Particulate composites; Physical Chemistry; Plastic deformation; Room temperature; Solid solutions; Solidification; Toughness
• ISSN: 1001-0521; 1867-7185
• DOI: 10.1007/s12598-024-02765-y

This study examines the microstructure, mechanical properties (with a focus on room-temperature toughness), and oxidation resistance of Ho-doped Nb–Si based in-situ composites. The base alloy consists of the coarse primary Nb 5 Si 3 phase and the Nb 5 Si 3  + Nbss (Nb solid solution) eutectic cells. Ho doping influences the solidification path. When the Ho doping is higher than 0.2 at%, the alloys transform into eutectic alloys. Ho can be solid-solved in trace amounts in the Nbss phase. However, most of Ho forms a stable Ho oxide phase, which alleviates oxygen contamination problem to some extent. Moreover, the interface separation between Ho oxide and other phases reduces the plastic deformation constraint. Thus, with 0.4 at% Ho doping, the K Q value is 18.03 MPa·m 1/2 , which is 31.1% higher than that of the base alloy. The strength of the Ho-doped alloys does not deteriorate with an increase in toughness. However, the large network-like Ho 2 O 3 in the 0.8Ho alloy causes a decrease in toughness and strength. In addition, the Ho oxide phase effectively blocks the inward oxygen intrusion. With 0.8 at% Ho doping, the oxidation mass gain per unit area is 10.16 mg·cm 2 , which is 39.7% lower than that of the base alloy. Graphical abstract