Effect of processing parameters on the density and microstructure of direct laser sintered Al-12Si powders

The effect of processing parameters on the sintering behaviour of gas atomised Al-12Si powders has been investigated. Laser power, scanning rate, scan spacing and layer thickness are found to control the densification and the resultant microstructural characteristics of the laser sintered parts. It was found that sintered density increased as the energy density increased reaching a maximum of 80.2% at an energy input per unit volume of 67 J mm^-3. For parts produced with a slightly lower power density (50 J mm^-3), the microstructure consisted of fine dendrites with interconnected porosity while parts fabricated with a slightly higher power density (100 J mm ^-3) were noted to have a preponderance of coarse dendrites with a discontinuous network of irregular shaped pores surrounded by a fully dense aluminium-silicon matrix.