W.M. Mao
,
Z.S. Zhen
,
H.T. Chen
,
X.Y. Zhong
金属学报(英文版)
With the help of an electromagnetic stirring device and alloy melt quenching technology, the microstructure of semi-solid AZ91D magnesium alloy slurry stirred by a rotationally electromagnetic field was studied and the experimental results are shown as the following. The primary α-Mg grains are refined obviously when the slurry is stirred by a rotational electromagnetic field during continuously cooling and they are eventually changed to fine rosette grains or spherical grains. If the above semi-solid slurry is further stirred isothermally for some time, much more spherical primary α-Mg grains can be obtained. If the melt is first cooled down to a given semi-solid temperature and then starts being stirred by the rotational electromagnetic field, the primary α-Mg dendrites will be large, and a longer time will be taken and a larger stirring power will be needed for the secondary arms of the dendrites to be remelted on the roots to prepare an ideal semi-solid slurry. Theoretical analysis indicates that the strong flow motion leads to a more even temperature field and a solute field and stronger man-made temperature fluctuation in the AZ91D magnesium alloy melt so that the spherical primary α-Mg grains are increased in the slurry. Moreover, all the measures promoting the temperature fluctuation will be favorable to the formation of spherical primary α-Mg grains and all the factors increasing the arm's root remelting difficulty will be favorable to the formation of rosette-type primary α-Mg grains.
关键词:
AZ91D magnesium alloy
,
null
,
null
W.M. Mao
,
A.M. Zhao
,
X.Y. Zhong
金属学报(英文版)
The nondendritic semi-solid slurry preparation of high chromium cast iron Cr20Mo2
has been studied in this paper. The experiments show that the proeutectic austenitic
particles are more spherical under a larger stirring power condition, even if the stirring
time is shorter, while the proeutectic austenitic particles are not very much spherical
under a smaller stirring power condition and some proeutectic austenitic dendrites
also exist, even if the stirring time is very long. The experiments also show that when
stirred for 5{6 minutes under the test condition, the semi-solid slurry with 40vol.%{
50vol.% solid fraction and spherical proeutectic austenite in the size of 50{80¹m can
be obtained.
关键词:
high chromium cast iron
,
null
,
null
