Recycling and Reuse of Metal Alloys by a Single Solid-State Additive Manufacturing and Repair Process

Additive Friction Stir Deposition (AFSD) provides a rapid, flexible, and robust metal recycling option that can be applied to manufacture large-scale multi-material components and/or repair damaged structures (i.e. vehicles, armor systems, etc.) while in-theatre, at the point-of-need, thus reducing the associated logistical challenges. This research report summarizes a combined experimental and computational investigation of two specific metal waste streams from the deployed Military Occupational Specialty (MOS) units: (1) scrap metal from machine chips generated by maintenance-MOS activities, and (2) expeditionary airfield (EAF) aluminum landing mats from EAF-MOS activities. These two waste streams typically generate chips and metal strips, respectively, and were used as the pilot case for feedstock in the AFSD process. Processing of the materials was performed on new and recycled feedstock material that allowed for the development of a Smooth Particle Hydrodynamic AFSD-Simulation tool to elucidate processing parameter influence on material flow, temperature, and localized stress and strain states. Additionally, multiscale characterization was performed from the nano- to the macroscale using a suite of analytical tools to understand intrinsic structural evolution of the as-deposited material. Furthermore, X-ray Computed Tomography (CT) analyses demonstrated that fully-dense epositions were achieved with isotropic mechanical behavior observed in a large 203 mm diameter by 44 mm tall helical build in large test articles. In addition, the in-depth experimental datasets characterizing microstructure, residual stresses, and mechanical performance were used to develop multiscale computational models for predicting material performance. To demonstrate the ability to recycle waste streams, strips were extracted from damaged airfields mats to use as a secondary feedstock to repair simulated forklift puncture damage on the aluminum airfield mat core top extrusion skin.