2.1 Micmstructures and mechanical pmpertieS
Before all the tests, annealing treatment of
300 "c x4 h was performed for ZElO magnesium alloy
sheets. Fig. 4 shows the microstructure of the annealed
ZElO alloy sheet. It can be seen that the grain
size is about 20 -30 km.
Figs. 5 (a) and (b) show the tensile properties of
the ZElO alloy sheets at elevated temperatures with
the velocity of 50 and 2.5 mm min- I , respectively.
It can be seen that the tensile strength decreases although
elongation increases considerably with an increase
in temperature, indicating obvious softening and
ductility enhancement at warm temperatures. The testing
velocity can bring about a difference in the ten-