Thermo-microstructural-mechanical modeling of the effect of wire diameters on single-bead Ti-6Al-4V wall deposits by laser wire deposition

Abstract

Six Ti-6Al-4V deposits with two geometries to extract tensile coupons from the build direction (Z) and travel direction (X), were produced by laser wire deposition (LWD) with different wire diameters. Inconsistent wall profiles were found for deposits produced with wire diameters of 1.1 and 1.6 mm due to the inhomogeneous melt pool sizes generated during the deposition process, indicating the unstable thermal history. It was found that increasing the wire diameter resulted in increased heat input, which produced coarser grains and resulted in decreased strength. Fractography analysis showed that greater amounts of defects were observed on the fracture surfaces of deposits produced with increased wire diameters, which weakened the tensile properties. The grain boundary $\alpha$ and the surrounding colony $\alpha$ facilitated crack propagation and caused early failure. This research also proposed a platform using modeling techniques to control cooling rates, microstructure ($\alpha /\beta$ phase fractions and $\alpha$ lath widths) and yield strength of LWD Ti-6Al-4V. The accuracy of all models was validated by comparing them with experimental data.