Original scientific paper
https://doi.org/10.30765/er.39.3.04
Effect of cooling rate on microstructure of B2-NiSc intermetallics
Zhipeng Yuan
; Henan Polytechnic University
Hao Chen
; Henan Polytechnic University
Hongbao Cui
; Henan Polytechnic University
Yatao Chang
; Henan Polytechnic University
Xuefeng Guo
; Henan Polytechnic University
Abstract
Ni-50at%Sc alloy was prepared by centrifugal
casting method. Volume fraction, the actual
content of B2-NiSc and second phase Ni2Sc in
alloy were analyzed with an Image-Pro Plus
software. The cooling rates for the solidified thin
plate with thickness of 2.65mm, 1.2mm, 0.75mm
and 0.35 mm are 1164, 2570, 4112 and 8811 K·s-
1, respectively. It is found that d=0.5 mm was an
critical dimension which corresponds to an abrupt
change in the solidification rate. It is also found
that (Ni2Sc+NiSc)eutectic was dispersed at grain
boundary or between dendritic arms due to the loss
of Sc element during melting. While d＞ 0.5mm
(corresponding to the thin plate with thickness of
0.75mm, 1.20mm and 2.65 mm), the solidification
structure consists of primary phase B2-NiSc and
(Ni2Sc+NiSc)eutectic. While d ＜ 0.5mm
(corresponding to the thin plate with thickness of
0.35 mm), the solidification structure is composed
of fine globular B2-NiSc and relatively small
amounts of (Ni2Sc+NiSc)eutectic. Based on the phase
volumetric analyzing of the microstructure with an
Image-Pro Plus software, the loss of Sc element
during melting was about 3.01~3.10 at%. The
eutectic NiSc in the lamellar eutectic structure
together with the primary phase B2-NiSc form a
larger single phase NiSc, while Ni2Sc with the form
of particles is distributed on the grain boundaries
after (970 ℃, 72 h) homogenization heat
treatment.
Keywords
centrifugal casting; B2-NiSc; microstructure evolution; rapid solidification; heat treatment; (Ni2Sc+NiSc)eutectic
Hrčak ID:
221127
URI
Publication date:
17.6.2019.
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