Liquidus projection of the Nb–Si–B system in the Nb-rich region

Alloys of the Nb–Si–B system have been evaluated aiming its use as high temperature structural materials. In this work the liquidus projection of the Nb–Si–B system in the Nb-rich region has been established based on the microstructural characterization of arc-melted alloys through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Six different primary solidification regions were observed: Nbss, NbB, T2 (αNb5Si3), Nb3Si, T1 (βNb5Si3) and D88. The following ternary invariant reactions are proposed to occur in the region of study: II1: L+NbB⇔Nbss+T2; II2: L+T1⇔Nb3Si+ T2; II3: L+Nb3Si⇔Nbss+T2; III1: L+NbB+D88⇔T2; III2: L+T1+D88⇔T2.