Microstructure of as-extruded AZ61 magnesium alloy was observed by optical microscope（OM）

and high strain impacting testing for the alloy was carried out by the Hopkinson bar to map the stress-strain curves at different strain rate.Dynamic stress-strain behavior of the as-extruded alloy was analyzed at high strain rate

and effects of strain rate on yield strength and crack mechanism were described.The results reveal that elastic modulus of the alloy exhibits somewhat change in the whole loading process

while obvious yield point can be observed in tensile testing.With increasing in strain rate

tensile strength of the alloy is increased with decreasing in mestable strain

however

absence of strain rate strengthening effects can be observed.The fracture morphology of the alloy was observed by SEM（scanning electron microscope）.It is found that tensile crack morphology of the as-extruded magnesium alloy is characterized by ductile fracture accompanying with a little cleavage fracture

showing the non-sensitivity for the strain rate.