International Journal of Minerals, Metallurgy and Materials
Volume 19, Number 9, Sep 2012, Page 836
DOI: 10.1007/s12613-012-0636-9
Corresponding author: Bao-yu Wang E-mail: bywang@ustb.edu.cn
© University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2012
Effect of cross wedge rolling on the microstructure of GH4169 alloy
Ning Zhang
1)
, Bao-yu Wang
1)
, and Jian-guo Lin
2)
1) School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
2) Department of Mechanical Engineering, Imperial College, London SW7 2AZ, UK
(Received: 15 October 2011; revised: 18 November 2011; accepted: 28 November 2011)
Abstract: The metal microstructure during the hot forming process has a significant effect on the mechanical properties of final products. To
study the microstructural evolution of the cross wedge rolling (CWR) process, the microstructural model of GH4169 alloy was programmed
into the user subroutine of DEFORM-3D by FORTRAN. Then, a coupled thermo-mechanical and microstructural simulation was performed
under different conditions of CWR, such as area reduction, rolling temperature, and roll speed. Comparing experimental data with simulation
results, the difference in average grain size is from 11.2% to 33.4% so it is verified that the microstructural model of GH4169 alloy is reliable
and accurate. The fine grain of about 12-15 µm could be obtained by the CWR process, and the grain distribution is very homogeneous. For
the symmetry plane, increasing the area reduction is helpful to refine the grain and the value should be around 61%. Moreover, when the
rolling temperature changes from 1000 to 1100ºC and the roll speed from 6 to 10 r⋅min
−1
, the grain size of the rolled piece decreases first and
then increases. The temperature may be better to choose the value around 1050°C and the speed less than 10 r⋅min
−1
.
Keywords: superalloys; nickel alloys; cross wedge rolling; microstructural evolution; grain size; numerical analysis
[This work was financially supported by the National Natural Science Foundation of China (No.50975023), the National Science and Tech-
nology Major Project (No.2009ZX04014-074), and Beijing Natural Science Foundation (No.3082013).]
1. Introduction
GH4169 alloy, a nickel-based superalloy, is widely used
in aeronautical and aerospace fields since it has very excel-
lent mechanical properties at high temperature [1-3]. How-
ever, GH4169 alloy possesses large deformation resistance,
poor technological plasticity, and a narrow processing tem-
perature range. When complex products of GH4169 alloy
are formed by forging or extrusion, there will be more
forming processes, lower tool life, and higher cost. There-
fore, in order to increase the productivity and reduce cost,
cross wedge rolling (CWR) was proposed to form products
of GH4169 alloy to give full play to the advantages of high
efficiency, high material utilization ratio, high quality, long
tool life, and so on [4-5].
Particularly, in the special working environment, prod-
ucts made of GH4169 alloy are strictly required to have fine
and homogeneous structure to bear the high creep load and
alternate stress [6]. However, GH4169 alloy is a single aus-
tenite structure that does not produce polycrystalline transi-
tion and phase recrystallization during the heating process,
so its grain size cannot be adjusted by heat treatment and
mainly relies on the hot working process [7]. That is, for
GH4169 alloy, process parameters directly determine the
microstructure of final products. Therefore, the CWR form-
ing process selected must be proper so as to control the mi-
crostructural evolution and get the ideal structure. Obviously,
it is extremely important to simulate the microstructural
evolution of GH4169 alloy during the CWR process,
through which reasonable CWR parameters could be ob-
tained to satisfy the actual requirements.
Recently, a good deal of research was carried out on the
simulation of microstructural evolution, whereas only a few
dealt with CWR. Wang et al. [5, 8-9] and Yan [10] simu-