Microstructure Evolution and Mechanical Properties of a Directionally Solidified Nb-Ti-Si-Cr-Al-Hf-Dy Alloy
Shenzhen Insititute, Peking University, Shenzhen 518057, China
* Corresponding author: firstname.lastname@example.org
The Nb-Ti-Si-Cr-Al-Hf-Dy alloy was prepared by conventionally casting and then directionally solidified (DS) with the optical floating zone melting technology. Microstructural evolution and mechanical properties of the as cast (AC) and DS alloys were studied by XRD, SEM, TEM, compression and bending tests. The results exhibit that α-(Nb, Ti)5Si3, (Ti, Nb)5Si3 and (Nb, Ti)ss phases formed the microstructure of the AC alloy, with precipitates of Cr2Nb, Dy2O3 and (Nb, Ti)3Si along phase or grain boundaries. The DS alignes (Nb, Ti)ss and α-(Nb, Ti)5Si3 lamellae parallel to the growth direction and refines the eutectic cell, but coarsens the primary α-(Nb, Ti)5Si3 phase. The DS alloy exhibits strong orientation of (310)(Nb, Ti)5Si3 and (110)(Nb, Ti)ss along the growth direction. TEM observation reveals that (Nb, Ti)ss and α-(Nb, Ti)5Si3 phases have an orientation relationship of (Nb, Ti)ss // α-(Nb, Ti)5Si3 and (002)(Nb, Ti)ss // (002)α-(Nb, Ti)5Si3. Compared with the AC alloy, the DS increases the mechanical properties of the alloy obviously and the alloy DS at 8 mm/h exhibits the best mechanical properties.
© The Authors, published by EDP Sciences, 2016
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