Effect of mixing time on the bed density, and microstructure of selective laser sintered (SLS) aluminium powders

The effect of mixing time on the homogeneity of aluminium powder blends and its SLS processed density and microstructure has been explored with a view to providing a basis for quality control. The degree of mixing of the powder particles was quantified in terms of the standard deviation of the bed density of the blended powder. The accuracy of the degree of mixing of aluminium powder's blends obtained at the optimum blending time of 10 minutes is determined by the powder properties and this significantly influenced the powder's bed density. By increasing the mixing time above 10 minutes, particulate agglomeration which inhibit good packing of powdered particles occurs, thus, sintered density decreases and porosity increases. Therefore, high porosity in the powder bed hinders effective thermal conductivity between aluminium particles, thereby, leading to deterioration of the sintered density and microstructure of the SLS processed samples.