3.2. Mechanical properties of as-ca

3.2. Mechanical properties of as-cast Mg-10Li-5Zn-xEr alloysThe density and hardness of the studied alloys are shown in Table 3. It can be seen that the density of the LZ105-xEr (x = 0, 0.5, 1, 1.5) alloys is almost the same about ~1.52 g/cm3. But the alloy's density reaches 1.545 g/cm3 with 3.5 wt% Er addition due to the greater relative atomic mass of Er element but its density is still 11.1% lower than that of pure magnesium (1.738 g/cm3). It's obvious that too much rare earth (RE) element addition is harmful to the low density of Mg-Li alloys. The hardness of the studied alloy increases with the increase of Er up to 0.5 wt% and then decreases.Fig. 8 shows that Er addition significantly improves the strength of LZ105 alloy but further increasing Er content leads to reduction of strength. The variation trend of elongation (EL) is nearly the same as strength. The optical yield strength (YS) and ultimate tensile strength (UTS) appear simultaneously with addition of 0.5 wt% Er, and the optical EL appears with 1 wt% Er addition. Therefore, the LZ105-0.5Er alloy exhibits an optimum combination of tensile properties with the UTS, YS and EL of 198 MPa, 223 MPa and 14.7%, which are improved by about 10.6%, 9.3% and 6.5% compared with those of LZ105 alloy (179 MPa, 204 MPa and 13.8%), severally.