Microstructure Evolution in Nb-12Si-22Ti-14Cr-2Al2Hf Alloy Fabricated by Directional Solidification

Abstract In this work, the microstructure evolution of the Nb-12Si-22Ti-14Cr-2Al-2Hf alloy (at.%) fabricated by liquidmetal-cooled directional solidification (LMC) was investigated and the solidification behaviors were discussed. The results revealed that the growth rate was of crucial in controlling the microstructure of this alloy and the higher growth rate was beneficial to the formation of metastable phase Nb ₃ Si. The microstructure of non-melted region consisted of Nb _SS dendrites, Nb _SS /Nb ₅ Si ₃ eutectics and Ti-rich Nb _SS /Cr ₂ Nb eutectics while the microstructure of quasi-steady-state growth region of this alloy consisted of Nb _SS dendrites, Nb ₃ Si laths and Ti-rich Nb _SS /Cr ₂ Nb eutectic. Nb ₃ Si had the advantage of nucleation at medium/high growth rate. Therefore, the microstructure evolution occurred in this study was owing to the increase of growth rate.