A multi-component evaporation model for beam melting processes

Abstract

In additive manufacturing using laser or electron beam melting technologies, evaporation losses and changes in chemical composition are known issues when processing alloys with volatile elements. In this paper, a recently described numerical model based on a two-dimensional free surface lattice Boltzmann method is further developed to incorporate the effects of multi-component evaporation. The model takes into account the local melt pool composition during heating and fusion of metal powder. For validation, the titanium alloy Ti–6Al–4V is melted by selective electron beam melting and analysed using mass loss measurements and high-resolution microprobe imaging. Numerically determined evaporation losses and spatial distributions of aluminium compare well with experimental data. Predictions of the melt pool formation in bulk samples provide insight into the competition between the loss of volatile alloying elements from the irradiated surface and their advective redistribution within the molten region.

Effect of Compositional Variation Induced by EBM Processing on Deformation Behavior and Phase Stability of Austenitic Cr-Mn-Ni TRIP Steel

“…Despite compositional variations upon AM (e.g., induced by the evaporation of Al and Mg) usually being unfavorable, as discussed in various studies, [50][51][52][53] the objective of the present work is the investigation of the impact of EBM processing parameters on the loss of Mn, the resulting mechanical response and phase evolution upon tensile testing. The results allow to evaluate if it is possible to manufacture specimens with locally differing properties by EBM from one initial pre-alloyed precursor powder material through a suitable setting of process parameters in order to realize functionally graded parts by chemical gradation.…”

Predictive Simulation of Process Windows for Powder Bed Fusion Additive Manufacturing: Influence of the Powder Bulk Density

“…The numerical framework is a 2D mesoscopic approach based on the Lattice Boltzmann method (LBM) designed for the simulation of powder bed fusion additive manufacturing processes [ 15 ]. It is capable of describing powder particle deposition [ 15 ], beam absorption [ 36 ], melt pool dynamics including wetting and capillarity [ 37 ], evaporation [ 38 ] with phase composition changes [ 39 ] and grain growth [ 40 ]. The LBM is a computational fluid dynamics method that does not solve the Navier–Stokes equation directly, but follows the microscopic Boltzmann equation with distribution functions.…”

S𝔸𝕄PLE: A Software Suite to Predict Consolidation and Microstructure for Powder Bed Fusion Additive Manufacturing

“…The saturated vapor pressure is calculated from the Clausius-Clapeyron equation. [36] However, not all of the particles that leave the fluid surface also leave the Knudsen layer above it. Some are back-scattered into the fluid.…”

“…Therefore, we apply a passive scalar transport algorithm that takes advantage of the fluid distribution functions known from the hydrodynamic calculation. [36] The mass change of one cell into its neighboring cell in direction i is δm ¼ f i ðxÞ À f¯iðx þ c i δtÞ, whereī denotes the direction opposite to i. If the mass change is negative, concentration streams out of cell x and into the adjacent cell.…”