Effects of RE content and heat treatment on microstructure and mechanical properties of Al-Mg-Si plate were investigated. The results reveal that mechanical properties of the plate sheet are improved with 0.2% RE addition in condition of T4 preageing and baking

where yield strength and tensile strength reach up to 281 MPa and 373 MPa

respectively

compared with those of ones without RE addition

increased by approximately 40 MPa and 30 MPa

respectively

showing improvement of strength and plasticity of the alloy with 0.2% RE addition. Although the alloy with 0.2% RE addition exhibits a higher elongation

yield strength and tensile strength is lower about 120 MPa and 40 MPa than those of T6 treated alloy in condition of T4 via baking. Fine and compact precipitates can be observed in the alloy after T4 preageing via baking

which results in the equivalent T6 treated alloy in tensile strength and the increase of 4% in elongation. The results show that the RE elernent play more positive role in improving properties of the alloy after preageing.