The material used in the present investigation
was a Mg-1 .O% Zn-O. 3% RE-O. 3% Zr alloy sheet
(mass fraction). The alloy was prepared by adding the
following alloying materials: commercial pure M g
(99. 9% Mg), Zn, Mg-20% Zr master alloy, and cerium-
rare earth (RE, mainly composed of 50.4% Ce
and 40.7% La). The alloy was held in the resistance
hrnace in a mild steel crucible and protected by CO,
and SF, mixed gases. The melt was held at 780 “c for
30 min to make the RE metal dissolve completely,
and then it was refined and cooled down to the pouring
temperature of 700 “c and cast into a permanent
mold. After it was homogenized at (410 + 5 ) “c for 8
h, the ingot was warm rolled at 300 - 420 “c to a
thickness of 1 .O mm with an average reduction ratio of
20% and a total reduction ratio of 95%.
All tensile tests were carried out on SANS
CMT5105 testing machine. The mechanical properties
of ZElO alloy sheets were examined at temperatures
ranging from 20 to 300 “c. The gauge length and the
width of specimens were 25 and 10 mm, respectively.
The CCV tests were performed on the universal
testing machine according to the GB/T 15825.6-1995
standard. Fig. 1 shows the schematic diagram of the
CCV test and the dimensions of die and punch. The
circular specimen had a diameter of 50 mm and a
thickness of 0.95 mm. When the test was conducted,
a circular sheet blank was placed on the top of the
die, which had a conical cavity and an underside cylindrical
hole at the center. Then the punch with the
spherical head moved down with a velocity of 2.5
mm - min- ’ to deform the sheet blank until it got
fractured. The measured critical diameter of the fractured
conical cup was defined as the CCV. For the
circular blank with a specified diameter, a smaller value
of CCV implied a larger drawing depth, resulting in
better formability. There was no blank-holder used in
the CCV test, so the effect of the blank-holder