Hybrid wire arc directed energy deposition and machining approach for realizing density-based functionally graded materials with enhanced strength-to-weight ratios

Abstract

Wire Arc Directed Energy Deposition (WADED), a high-deposition-rate Additive Manufacturing (AM) technique, enables the rapid fabrication of near-net-shape metallic components. However, achieving Functionally Graded Materials (FGMs) with density variations within the same material remains challenging. This study introduces a novel Hybrid WADED (H-WADED) process to fabricate mono-material FGMs with engineered density gradients tailored for applications in aerospace, nuclear energy, and electromagnetism. In this method, each layer is deposited using WADED, followed by face milling and robotic drilling to introduce controlled holes. The diameter and spacing of the holes are designed to achieve the desired density gradient, enabling up to a 10 % reduction in mass. Experimental results showed 2 mm diameter holes as optimal, minimizing material flow and distortion while improving the strength-to-weight ratio. This innovation also enhances thermal dissipation capabilities, making the components suitable for high-stress environments. Performance evaluation of the fabricated FGMs revealed a 26.2 % reduction in thermal conductivity and significant mitigation of residual stresses due to stress redistribution around the holes. Under compressive loading, the samples exhibited a maximum load capacity of 200 kN. Although tensile strength was reduced by 19.6 % compared to solid samples, elongation remained unaffected, highlighting the structural integrity of the components. This work demonstrates an effective method to fabricate density-based FGMs, providing a practical pathway for developing advanced, lightweight, and thermally efficient components for critical industrial applications.