Effect of titanium and molybdenum on the structure and mechanical properties of an in situ composite based on the niobium-silicon system

Abstract

Composites of the Nb-Si-T-Zr-Hf-Cr-Al-Mo-Y system of three compositions differing only by their ratios of molybdenum and titanium content (13 at % Ti + 8.5 at % Mo; 15 at % Ti + 6.5 at % Mo; and 17 at % Ti + 4.5 at % Mo) are investigated. Composite samples are prepared via directional solidification at a pulling rate of 5 mm min^–1. The main structural components of the composite are Nb _ss -based solid solution and solid solution based on intermetallic compounds Nb₃Si, β-Nb₅Si₃, and α-Nb₅Si₃. According to data from short-term strength tests at 1300 and 1350°C, the average values of the short-term flexural strength drop as the molybdenum content falls and the titanium content rises from 950 to 707 MPa and from 562 to 433MPa. The rate of creep deformation at 1300°C and a stress of 200 MPa rises from 9.8 × 10^–5 to 10.6 × 10^–3 h^–1.