Microstructure and high-temperature mechanical properties of Nb-silicide based in-situ composites
(1.School of Materials Science and Engineering, South Campus, Shandong University, Ji’nan 250061, China
2.School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
3.北京市北京航空航天大学材料科学与工程学院)
2.School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
3.北京市北京航空航天大学材料科学与工程学院)
Abstract: Nb-15W-18Si-xHf (x = 0, 5, 10 and 15, mole fraction, %) alloys were prepared by arc melting and then homogenized at 1 750 ℃ for 50 h. The microstructure and mechanical behaviors, such as Vickers hardness, fracture toughness, room- and high- temperature strength of the alloys were investigated. The microstructure of the annealed Nb-15W-18Si-xHf alloys is composed of large primary NbSS dendrite and fine eutectic mixture of NbSS and M5Si3 silicide. Both the hardness and the fracture toughness show an increase tendency at room temperature with increase of Hf content. The 0.2% compressive yield strength, σ0.2 of the alloys with 5 %Hf and 10%Hf are larger than 960 MPa at 1 200 ℃, and about 500 MPa even at 1 500 ℃.
Key words: Nb-15W-18Si-xHf alloys; niobium; silicide; microstructure; strength; fracture toughness