Made to Measure…Aluminium

Who are you?: Emma Ryan
What is your role?: EngD Researcher
What?: Wire Arc Additive Manufacture of Aerospace Aluminium Alloys

WAAM

Figure 1: A WAAM fabrication cell. Showing the robot arm, the welding torch head on the end of the arm and what is, in this case, a rotatable platen for deposition.

I beg your pardon?: Additive manufacture refers to a process of depositing a material to make objects from a 3D computer model, usually layer upon layer. It is different to many conventional methods as it is not subtractive. There are many different types of additive manufacture such as 3-D printing (binder and material jetting techniques), laser sintering (powder-bed fusion techniques) and wire arc additive manufacture (directed energy deposition techniques).  The focus of my project is on wire arc additive manufacture (WAAM). WAAM is a process where a welding torch is used to produce an arc: wire is fed through it so that weld beads are deposited onto a substrate. Subsequent layers are deposited in order to form a near-net shape part.
OK, Why?: WAAM has a high ‘buy-to-fly’ ratio, or in other words, little material is wasted. This is an advantage common to all additive processes. Unlike some other processes, the deposition rates are high. Due to the near-net shape produced, both material waste and lead-time are reduced and considerable cost reductions can be made.
And?: A lot of work has been carried out on high strength aerospace aluminium because of its current use for conventionally manufactured parts built by Lockheed Martin, particularly forgings (although I can’t say too much about the parts themselves!) and its ready availability (you can buy aluminium welding wire ‘off the shelf’). Current use of aluminium for conventional parts is due to various desirable properties including low density, high specific strength, reasonable corrosion resistance and relatively low cost.
So what?: There are challenges involved with making WAAM applicable for industrial purposes. Studying the effect of variables of the WAAM process is required in order to determine critical variables to control and monitor for certification purposes. Repeatability of the process needs to be ensured for certification purposes. Significant porosity is currently found in WAAM parts which needs to be reduced to improve mechanical properties and reduce the risk of failure.  Currently, I am analysing the influence of wire quality on the stability of the WAAM build and the resulting mechanical properties in the part. It is known that the wire quality can affect WAAM (the stability, repeatability and mechanical properties of the part) and cause porosity. My work is contributing to the goal of knowing how good the materials properties will be, and just as importantly, what steps need to be taken to make these properties reproducible.

Final Thought: A better understanding of the influence of wire quality on WAAM can provide ‘made to measure’ aluminium components.