Synergistic effect of Zr and Ti on microstructure and properties for Nb Si based in-situ composites

To reduce the adverse effects of highly active titanium elements in Nb Si alloy, a series of high content of Zr and Zr for Ti substitution in Nb Si based alloys are studied. The results show that the addition of Zr changes the solidification path from hypoeutectic to eutectic. The fracture toughness significantly enhances in 24Ti- xZr ( x = 0, 4, 8, 16) alloys, owing to the increase of Nbss phases and microstructure refinement in the matrix. Moreover, the room-temperature compression properties increase in 24Ti- xZr alloys, resulting in the effect of significant solution strengthen. In 24Ti 16Zr alloys, three-types of Nbss/Nb ₅Si ₃ eutectic are found, resulting in large supercooling degree and rapid cooling condition. The maximum K _Q value and compressive strength are 12.47 MPa·m ^1/2 and 1800 MPa respectively in 24Ti 16Zr alloys. The K _Q values in Nb-16Si-(24- x)Ti- xZr ( x = 4, 8, 16, 24) alloys enhance with element Zr increases to 16 at.% and then decline slightly, suggesting that appropriate substitution of Zr for Ti is effective for promotion of toughness. It`s owing to the formation of complex Nbss/(Nb, X) ₅Si ₃ eutectic. The high-temperature compressive strength is also prepared (1200 °C), element Zr can provide a signally work hardening by making a strong cooperative deformation of Nbss and γNb ₅Si ₃ phases, and the highest true stress values are found in 8Ti 16Zr alloys.