Analytical modeling of multi-track powder-fed laser directed energy deposition: On the relationships among process, deposition dimensions, and solidification microstructure in additively manufactured near-β titanium alloy

Abstract

Scanning strategies can significantly affect temperature distribution and location-specific variation of solidification microstructure in laser-directed energy deposition by powder-feeding (LDED-PF). In this paper, a physics-based analytical model of multi-track LDED-PF is developed to rapidly predict the temperature field of cuboidal geometries under four different scanning strategies: bidirectional, unidirectional, inward spiral, and S-pattern. Based on 2D thermal models, a new universal algorithm is developed to predict the geometrical profile of the overlapping beads, applied to all scanning strategies. The effects of four scanning strategies on the temperature field, geometrical profile, and microstructural behavior are investigated and tested. The linkages between the process and solidification microstructure are revealed and rationalized through temperature simulations and microstructural characterization. The developed model is tested for multi-track deposition of near- β titanium (Ti-5Al-5 V-5Mo-3Cr) alloy at different laser powers, scanning speeds, and step-over distances under different scanning strategies. The solidification maps are established for the alloy, and the microstructural evolution of columnar to equiaxed transition (CET) is predicted. The results indicate that the model can ideally predict the deposition dimensions, temperature field, and solidification microstructure. This modeling methodology is applicable to other metallic materials, and it can be used to manipulate and engineer the location-specific variation of solidification microstructure.