Microstructure evolution and mechanical properties of ZrC-added Nb–16Si–20Ti alloys

Abstract

The effect of ZrC addition on the phase composition, microstructure, and room-temperature mechanical properties of arc melted Nb–Si–Ti based alloys has been systematically investigated. The results indicated that the addition of ZrC promotes the decomposition of (Nb,X)3Si phase. The addition of ZrC promotes the microstructure transformation from hypoeutectic to hypereutectic, and the eutectoid reaction of (Nb,X)3Si to Nbss/(Nb,X)5Si3 eutectic structure. The KQ value of Nb–16Si–20Ti–1ZrC alloy is the highest, reaching 13.9 MPa m1/2. The decomposition of (Nb,X)3Si phase can increase the room-temperature fracture toughness. However, the precipitation of primary γ-(Nb,X)5Si3g-b phase deteriorates the room-temperature fracture toughness. Meanwhile, the more the content primary γ-(Nb,X)5Si3g-b is, the lower the room-temperature fracture toughness is. The maximum compressive strength of Nb–16Si–20Ti–1ZrC alloy is 2331 MPa, and the fracture strain of Nb–16Si–20Ti–3ZrC alloy is 11.4%. The fracture morphology of Nb–16Si–20Ti based alloys with ZrC additions is a brittle quasi-cleavage fracture.