The microstructure optimizing of the Nb–14Si–22Ti–4Cr–2Al–2Hf alloy processed by directional solidification

In this work, the microstructure evolution of an Nb–14Si–22Ti–4Cr–2Al–2Hf alloy processed by liquid-metal-cooled directional solidification (LMC) and heat treatment (HT) was investigated. The microstructure in the quasi-steady-state growth region of the LMC ingot consisted of primary (Nb,Ti)SS dendrites and eutectic (Nb,Ti)SS/(Nb,Ti)5Si3. The unstable (Nb,Ti)3Si phase was eliminated and the eutectic with coupled (Nb,Ti)SS and (Nb,Ti)5Si3 occurred. After heat treatment of selection, the fiber reinforcing mash structure was maintained: the (Nb,Ti)SS phase connected to be a continuous matrix and the fine discontinuous fibrous (Nb,Ti)5Si3 was distributed uniformly and parallel to the growth direction on longitudinal section.

► The Nb–14Si–22Ti–4Cr–2Al–2Hf alloy was directionally solidified by LMC.
► Microstructure evolution was investigated.
► Desired microstructure: continuous matrix (Nb,Ti)SS+fine discontinuous fibrous (Nb,Ti)5Si3.
► The desired fiber reinforcing mash structure was obtained.