The effects of different selective laser melting（SLM） parameters on relative density of SLM-processed rare earth modified Al-Mn alloy were investigated and the optimum parameters were presented. On this basis

the influence of heat treatment on mechanical properties of SLM-formed Al-Mn-Sc-Zr alloy was explored. The results indicate that a excessive applied laser energy density（E）leads to the spherical pores inclusion inside

which is attributed to the constituent evaporation. A low E results in the limited overlap ratio

leading to the formation of irregular pores. When E is optimized to 52.6 J/mm

3

the internal defects of SLM-processed parts are reduced with improved densification level of 99.8%. Two kinds of grain morphology can be observed in the molten pool: equiaxed grains generated at the bottom and columnar grains at the center. Tensile properties and micro-hardness of the alloy can be improved effectively by heat treatment. After annealing at 300 ℃ for 4 h

specimens exhibit excellent tensile properties

where tensile strength reaches 756 MPa and elonagation is 11%.The micro-hardness of the as-deposited specimens are 131.2 HV

0.2

whereas that annealed at 280 ℃ for 6 h is 178.3 HV

0.2

.