Effects of Ca addition（0.1%

0

.5%）on solidified structure and mechanical properties of AZ91 magnesium alloy were analyzed by OM（optical microscopy）

XRD（X-ray diffraction）and SEM（scanning electron microscopy）.The results show that primary phase in the AZ91 alloy is coarsened with adding trace Ca.With the increase of Ca addition

change of primary phase can be ignored

however

second phase is refined firstly and then coarsened

where secondary phase size exhibits desirable with0.4% Ca addition.Al2 Ca phase can be found with 0.5%Ca addition.The solid-liquid transition temperature range of the alloy becomes narrow

and the eutectic transition temperature is increased with adding0.4%Ca.With the increase of Ca addition

mechanical properties of the AZ91 magnesium alloy are increased.Comprehensive mechanical properties exhibit satisfied when Ca addition is 0.4%

where tensile strength and elongation of the alloy reach 261 MPa and 14.8%

increased by 51% and 691%

respectively

compared with the alloy with absence of Ca addition.