Non-beam-based metal additive manufacturing enabled by additive friction stir deposition

Additive Friction Stir-Enabled Solid-State Additive Manufacturing for the Repair of 7075 Aluminum Alloy

“…In order to repair various types of volume damages in AA 7075-including keyholes, long grooves, large-scale corrosion or wear damages-it is vital to develop a versatile solid-state technique that can continuously supply filler material, while also allowing for digital control of the material addition and repair paths. Such a technique remained elusive until the recent emergence of a solid-state metal additive manufacturing technique-additive friction stir deposition [24][25][26]. Additive friction stir deposition integrates the friction stir principle with a robust material feeding mechanism to enable site-specific deposition.…”

“…It leverages the benefits of friction stir-e.g., in the prevention of hot cracking, high residual stresses, and void formation-while providing the additional capability of adding material for a more robust repair of volume damages. The current tool size in additive friction stir deposition enables a high build rate, 10 3 cm 3 /h for Al alloys [24], which is uniquely suitable for the large-scale repair of AA 7075.…”

Additive friction stir deposition: a deformation processing route to metal additive manufacturing

“…The current tooling size results in wide deposition tracks on the order of centimeters, allowing for high build rates and good scalability. That being said, this also suggests limits on the smallest attainable feature size [30]. Overall, rather than producing complex geometries with small feature sizes, AFSD is better suited for large-scale additive manufacturing in which structural integrity is a must.…”

“…Inspired by solid-state welding, several deformation-based metal additive manufacturing approaches have emerged during the last few years [25]. These include ultrasonic additive manufacturing [26,27], cold spray additive manufacturing [28,29], and additive friction stir deposition (AFSD) [30,31]. Without material melting, these approaches exploit deformation bonding to implement layer adhesion via ultrasonic vibration, particle impact, and friction stirring, respectively.…”

“…First, ultrasonic additive manufacturing is a hybrid technology based on initial ultrasonic welding of foils followed by CNC (computer numerical control) machining, whereas AFSD is a freeform fabrication process that enables printing at specific locations. Second, cold spray additive manufacturing often leads to incompletely bonded interfaces between particles, resulting in porosity and micro-cracks [32,33]; in contrast, AFSD typically renders fully-dense parts in the as-printed state [30,34]. Third, while ultrasonic additive manufacturing, cold spray additive manufacturing, and AFSD are all based on deformation bonding, the former two only involve local plastic deformation around the interface or particle contact regions.…”