Abstract
This study shows that a dry mix of aluminum (Al) and Poly(ethylene terephthalate) (PET) powders can be successfully used for freeforming with powder bed fusion (PBF). The Al-PET powder had a narrower processing window than PET powder, which was due to the Al particles acting as a nucleating agent, thus shifting the melt crystallization temperature to higher values. However, with some process adjustments, curl could be overcome and tensile bars and complex shapes could be printed. While the tensile modulus of the Al-PET composites was higher than PET, the tensile strength and impact resistance decreased. This performance was unlike our previous work of injection moulding (IM) of the same Al-PETs, where an unusual simultaneous increase in tensile modulus, tensile strength, and impact resistance occurred. The reason for the decrease in the tensile strength and impact resistance in Al-PET articles made by PBF was the voids that were inherent from the PBF process, and the added interfacial voids that sometimes occurred between Al particles and PET. Nevertheless, besides the freeforming capability, the advantage of PBF over IM for making Al-PET composites is the crystallization of the PET phase in the article, which is more difficult to achieve with PET by IM. With further optimized compositions of Al-PET, freeform printing of thermally conductive and heat dissipating articles should be possible.