Large-scale solid-state metal additive manufacturing for quality and supply chain sustainability

The mainstream fusion-based metal additive manufacturing processes like powder bed fusion and directed energy deposition are based on melting and rapid solidification. Potentially viewed as a sequence of mini-casting processes, they suffer from critical issues such as hot cracking, porosity, and high residual stress. These issues can be fundamentally addressed by employing a large-scale solid-state additive process, additive friction stir deposition (AFSD), which combines the friction stir concept with material feeding to enable printing and free forming in specific locations in 3D space. Characterized by extreme thermomechanical processing conditions, AFSD eliminates the porosity in the feed material, modifies the microstructure, and can result in superior mechanical performance after additive manufacturing and additive repair. With significantly improved energy efficiency and high tolerance with the feedstock forms, AFSD can also play a significant role in addressing the supply chain issues, especially for large-scale forged components in aerospace, transportation, heavy equipment, and power generation, which require long lead times to import large tooling from overseas. In this presentation, I will offer an up-to-date summary of the current status of the AFSD research process, including an analysis of the process physics observed through in-situ monitoring, the study of material flow using time-resolved characterization, the evolution of dynamic microstructure, and niche applications, such as structural repair, material recycling and upcycling, and selective-area cladding. Furthermore, I will explore prospective applications of AFSD in enhancing the sustainability of supply chains. Our analysis indicates that the AFSD plan could substantially reduce lead times from 2-3 years to mere weeks or months, thereby creating stable supply chains with consistent product quality and availability amidst an increasingly unpredictable global environment.