High fidelity thermo-mechanical model of in-situ micro-rolling in laser-directed energy deposition: multi-track multi-layer case

Abstract In-situ rolling during Directed Energy Deposition (DED) at elevated temperatures has been shown to enhance build quality. However, experimentally characterizing the deformation mechanisms that drive these improvements remains challenging. While previous thermo-mechanical finite element analyses (FEA) have focused on single-track and thin-wall multi-layer cases, the more realistic multi-track, multi-layer scenarios remain largely unexplored. This study develops and validates an FEA framework for in-situ rolled DED in a three-track, three-layer Ti-6Al-4V deposition, achieving thermal predictions with95% accuracy against experiments. Unlike single-track multi-layer cases reported in the literature, where in-situ rolling significantly influences thermal behaviour, its impact in the multi-track scenario is minor due to increased lateral heat diffusion. In-situ rolling effectively induces compressive plastic strain across all three layers, significantly mitigating tensile residual stresses that typically develop in unrolled cases. Furthermore, the study reveals that deposition and in-situ rolling at the top have a more pronounced influence on thermal and deformation cycles than at the side. These findings provide valuable insights for optimizing multi-track, multi-layer DED, enabling improved metallurgical and mechanical properties in additively manufactured components.