Morphology and Tensile Behavior of 2024 Al Alloy Objects Fabricated by Uniform Droplet Spraying Deposition

A metal rapid prototyping technique, uniform droplet spraying, is utilized to fabricate 2024 Al alloy objects. Molten droplets are generated by drop-on-demand mode and deposited onto a zigzag moving substrate, which produces objects with different side surfaces. The tensile strength of the deposited specimen is 180.5 MPa, with elongation to fracture of ~8.2%. The fracture surface of deposited specimen presents two regions, namely, rough region and smooth region. The smooth region initially cracks under tension load, and the rough region presents many elongated dimples, indicating a ductile shear fracture. This unique tensile behavior could be attributed to weak metallurgical bonding between droplets and the special movement of substrate.