Understanding size-dependent thermal, microstructural, mechanical behaviors of additively manufactured Ti-6Al-4V from experiments and thermo-metallurgical simulation

Size and build strategy effects for the L-PBF process applied to Inconel 625 vertical struts: a combined numerical and experimental approach

“…For instance, average temperatures vary between 320 K (~50°C) for the smaller diameter (0.25 mm) and 520 K (~ 240°C) for the larger (D = 2 mm), with an OI contour strategy (Figure 11). Such temperatures are in the same order of magnitude as those evidenced by Promopattum et al [17] on a titanium alloy (60°C -120°C).…”

“…Such cooling rates are approximately ten times lower than those estimated by Scipioni-Bertoli with an analytical Rosenthal model [15]. They are also two times lower than data obtained by Promappatum et al [17] in their modeling work. However, such a difference may be explained by the two to three times lower scan speeds used in the current work, and by the fact that we considered such solidification conditions 60 µm below the surface i.e in areas non-remelted by subsequent layers.…”

“…To fulfill the requirements of such a model, a two-step approach derived from Promopattum's work [17] is proposed:…”

“…In the high-resolution single-layer model (SLM), the powder bed was considered part of the computational domain, to provide realistic interface losses. For each strut of strut radius, a 1 mm equivalent powder bed width was added around the strut (Figure 2b), using a similar geometrical approach to [17]. For instance, the mesh domain of a 2 mm diameter strut surrounded by the powder bed corresponds to a 4 mm diameter (2 mm + 2 x 1 mm), whereas the mesh domain of a 0.5 mm strut + powder bed has a 2.5 mm diameter (0.5 mm + 2 x 1 mm).…”

“…Promoppatum et al [17] have carried out an interesting numerical thermo-metallurgical modeling of small L-PBF struts, including size effects, and taking into account solid phase transformation. They have confirmed numerically the reduction of Ti- lath width with a decrease of diameters, and predicted with a correct agreement the resulting increase of yield strength.…”