Purpose
Additive manufacturing (AM) can achieve significant weight savings with only minor compromises in strength if high-performance wrought aluminum alloys are used as feedstock. Despite the advantages in strength that aluminum alloys (AA) 6061 offer, they cannot be manufactured via printing because of hot cracking and other solidification problems. The purpose of this study is to achieve high-quality printing of AA6061 with nanotreated wires.
Design/methodology/approach
Nanotreating was used to modify the AA6061 alloy composition by adding a small fraction of nanoparticles to enhance the alloy’s manufacturability and resultant properties. Wire arc additive manufacturing (WAAM) was used to print the nanotreated AA6061 wire feedstock. The microstructure of the printed AA6061 was characterized by X-ray crystallography, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy mapping. The microhardness profile, tensile behavior and fracture surface were analyzed.
Findings
This work successfully used WAAM to print nanotreated AA 6061 components. The resulting AA6061 parts were crack-free, with exceptional grain morphology and superior mechanical properties. Owing to the excellent size control capabilities of nanoparticles, a homogeneous distribution of small grains was maintained in all deposited layers, even during repeated thermal cycles.
Originality/value
Previous studies have not successfully printed AA6061 using WAAM. Conventional WAAM products exhibit anisotropic mechanical properties. The nanotreated AA6061 was successfully printed to achieve homogeneous microhardness and isotropic tensile properties. The promising results of this study reflect the great potential of nanotech metallurgy as applied to the WAAM process.
We report the dissimilar joining of aluminium alloys 6061 and 7075 using filler rods nano-treated with TiC nanoparticles. TiC enables the formation of a fine and equiaxial weld metal microstructure while preventing the formation of hot cracks. Dissimilar joints were also naturally aged, and their strength evolutions were tracked over 8 weeks and compared to a nano-treated, homogeneous AA7075 joint. Heterogeneous weld metals regained over 30 HV with a mix of MgZn 2 and Mg 2 Si strengthening phases. Nano-treatment thus shows great promise, being able to facilitate the fusion welding of a traditionally difficult-to-weld system and enable a natural aging response between two artificially aged alloys.
High-strength Al-Zn-Mg-Cu alloys such as AA7075 have drawn considerable attention and interest from both industry and academia owing to their high specific strengths and good fatigue resistance. Wire-arc directed energy deposition (DED), an emerging near-net-shape manufacturing technology, faces significant challenges in printing AA7075 due to its hot cracking susceptibility. In this study, we use nano-treated AA7075 wire as feedstock to additively manufacture a crack-free deposition of the high-performance alloy. After T6 heat treatment, the nano-treated AA7075 achieves exceptional yield strength (510.3 MPa), ultimate tensile strength (606.0 MPa), and elongation (12.6%). In addition, nanoparticles homogenize the microstructure upon solidification and inhibit grain growth from cyclic thermal exposure, yielding refined, equiaxed grains throughout the deposition and enabling isotropic mechanical properties in both as-built and T6-treated conditions. Thus, this study highlights a promising intersection of nano-treatment and wire-arc directed energy deposition for printing traditionally unprintable materials.
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