Effects of grain refiner on microstructure and mechanical properties of the Al-Mg-Zr alloy were investigated by adding trace Sc or Ti elements and compound adding Ti and Sc.The results show that the addition of 0.15%Ti can positively refine microstructure of the alloy and improve mechanical properties obviously.And the combined addition of 0.2%Sc and 0.15%Ti exhibits the desirable grain refining effect

where average grain size of the alloy is refined to only about 43μm

and the strength and elongation are improved by about 70%and 16.4%

respectively

which is largely attributed to the formation of Al3 Ti

Al3Sc

Al3（Ti

Zr）

Al3（Sc

Zr）and Al3（Sc

Ti）particles commonly to act as heterogeneous nuclei and to promote the grain refinement.