Tensile properties of aluminium 4047A built in droplet-based metal printing

Abstract

PurposeDirectly printing molten metal droplets on a build platform to create full dense metal parts is a promising additive manufacturing process. This study aims of to analyse the effects of the thermal conditions on the resulting tensile properties of parts made from aluminium 4047A built in droplet-based metal printing.Design/methodology/approachA drop-on-demand print head with pneumatic actuation is used to eject droplets on a nickel sheet mounted on the heated build platform. Tensile specimens are machined from cuboid blocks built by successive droplet deposition and tested in a universal testing machine. The ultimate tensile strength, uniform elongation and yield strength are evaluated and presented. Micro-sections are taken from the printed blocks to examine the internal pores and the metal’s microstructure.FindingsWith an increase in the interface temperature the uniform elongation increases from 0.5 to 12%, while the yield strength decreases from 130 to 90 MPa. The ultimate tensile strength increases from 130 MPa to a maximum of 190 MPa at an interface temperature of 530º C and slightly falls for higher interface temperatures. Those values are in the same range as conventionally casted parts of the same alloy. The authors’ hypothesis is that the main effect responsible for the mechanical properties is the wetting of solid material by the liquid droplet and not remelting, as has been reported in literature.Originality/valueTo the best of the authors’ knowledge, this is the first time that mechanical properties of aluminium 4047A built by a droplet-based additive manufacturing process are published for different interface temperatures. It is also the first time that the main effect on mechanical properties is attributed to wetting instead of remelting.