Mechanical properties of directionally solidified Nb–Mo–Si-based alloys with aligned Nbss/Nb5Si3 lamellar structure

The room-temperature fracture toughness and high-temperature compression strength are investigated in directionally solidified Nb–Mo–Si-based alloys with aligned Nbss/Nb5Si3 lamellar structure. The fracture toughness is higher as grain size is reduced or annealing at 1300 °C for 100 h is applied. The normalized work of rupture (χl) in the in situ Nbss/Nb5Si3 lamellar structure is modeled and calculated to range from 0.10 to 0.38. Besides, the Nbss and Nb5Si3 are firmly connected on the fracture surface. Thus, the Nbss/Nb5Si3 interface is strongly bonded. Either reducing interface toughness or enhancing Nbss toughness is advantageous for interface decohesion. In the annealed Nb–17Si–10Mo–0.1Ga alloy, a small amount of Nbss/Nb5Si3 interface decohesion is observed because the annealing increases the toughness of Nbss. At 1250 °C and 1350 °C, the maximum compression strength is 620 MPa and 520 MPa, respectively.