The microstructure

tensile properties and damping capacity of cast Mg-11.3Gd-1.2Y-1.1Al

Mg-15.6Gd-1.2Y-1.0Al

Mg-17.5Gd-1.1Y-1.0Al and Mg-13.2Gd-2.9Y-0.9Al alloys were investigated by tensile testing

XRD（X-ray diffraction）

OM（optical microscopy）and SEM（scanning electron microscopy）.The results indicate that the cast Mg-Gd-Y-Al alloys consist ofα-Mg

Al2（Gd

Y）and Mg24（Gd

Y）5 phases.After solution treatment

strip-like LPSO compounds appear in grain.The tensile properties of as-cast Mg-Gd-Y-Al alloys have close relation with the total content of RE element.A higher total content of RE elements corresponds to the higher strength and lower elongation.After T4 treatment

the yield strength of the alloys is decreased slightly

and the ultimate tensile strength is increased slightly

while the elongation is improved significantly.After T6treatment

the yield strength of the alloys is increases significantly.The yield strength of higher RE containing alloy is increased more than 80MPa.The damping capacity of as-cast Mg-Gd-Y-Al alloys is decreased with the increase of Gd addition

while the T6treatment can obviously increase the damping capacity.The damping ratios P0.1of the four alloys are in range of 4.92%

8

.22%

belonging to middle damping capacity.The three alloys with higher RE content in total have high yield strength of 230 MPa and good damping capacity in T6 condition

and are the high strength cast Mg alloys with suitable damping capacity.