Laser directed energy deposition additive manufacturing using friction stir channelling extruded wire

This paper investigates a new ‘forged’ wire additive manufacturing processing, in which the metal wire is produced as a by-product from stationary shoulder friction stir channelling (SS-FSC) under the severe plastic deformation mechanism (known as CoreFlow®), and then used as the feedstock in directed energy deposition with a laser beam and wire feedstock (DED-LB/w) additive manufacturing. For the first time, the ‘by-products’ produced in the SS-FSC process, which are ‘forged’ 6082 aluminium alloy wire, were tested with built-tracks using DED-LB/w. Process mapping was built to demarcate the melting states, including the stable, dripping, and incomplete melting regimes, over a wide range of laser energy densities (92 to 303 kJ · s · g − 1 · cm − 2 ). Metallurgy tests were also conducted to reveal the evolution of the microstructure and defect formation of the deposited tracks. It was found that: (i) Stable deposition with a grain size of 9 − 20 μm can be achieved with optimised processing parameters, i.e., energy density 243 kJ · s · g − 1 · cm − 2 with a laser power 3.8 kW , a scanning speed 0.8 cm · s − 1 and a wire feed rate 2.0 cm · s − 1 ; (ii) The substructure morphology is gradually transitioned from columnar at the track bottom to cellular ( 8.9 ± 1.8 μm ) at the top, driven by an increased cooling rate; and (iii) The built track porosity is mainly composed of gas pores that are small (equivalent diameter of 20 − 50 μm ) and spherical, primarily resulting from the ambient gas, the SS-FSC extruded wire oxides and contaminations. The study supports resource-efficient, low-carbon manufacturing via reuse of by-products, in alignment with the Net Zero Strategy. • Directed energy deposition employs novel friction stir channelling extruded wire. • Process mapping is built to demarcate melting regimes based on processing parameters. • Fine grain size (9–20 μm ) is achieved in the additive builds though with porosity. • Gas entrapment and oxides are identified as the primary sources of porosity.