Microstructures and properties of Nb–Si-based alloys with B addition

The Nb–16Si–18Ti–xB (at%, similarly hereinafter, x = 0, 1, 2, 3) alloys were prepared by arc melting in a water-cooled copper crucible. The influences of B addition on their microstructures and properties were based on the data of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and electronic universal material testing machine. It is found that the addition of B promotes the formation of α-Nb₅Si₃ phase and suppresses the formation of Nb₃Si phase. B addition also tends Nb–16Si–18Ti alloy to form the hypereutectic structures. The content of silicide phases shows a trend of firstly decreasing and then increasing in Nb–16Si–18Ti–xB (x = 0, 1, 2, 3) alloys. The size of Nb solid solution (Nb_ss) phase increases in Nb–16Si–18Ti–xB (x = 0, 1, 2, 3) alloys after heat treatment at 1523 K for 10 h. The room temperature compression strength of Nb–16Si–18Ti alloy increases firstly and then decreases with B addition. The high-temperature compression strength of Nb–16Si–18Ti alloy decreases firstly and then increases with B addition. It is found that the volume and size of silicide phases have a synergistic effect on the compression strength of Nb–Ti–Si-based alloys.