Multiphase mesoscopic simulation of multiple and functionally gradient materials laser powder bed fusion additive manufacturing processes

Abstract

Multiple material laser powder bed fusion (MMLPBF) is a recently developed technology that broadens the application range of additive manufacturing. Experiencing dissimilar materials interactions, the physical phenomena in the MMLPBF process are more complex. In this study, a computation fluid dynamic model in the mesoscale for simulating single-track MMLPBF melt pool behavior is developed. The characteristics of melting IN718/Cu10Sn powder beds were investigated. It is shown that in melting a mixed IN718/Cu10Sn powder bed, the temperature of the melt pool decreases with increasing Cu10Sn fraction, owing to the difference in the thermal–physical properties of dissimilar metals, particularly the melting points, laser beam absorptivity and thermal conductivity. A braze zone is formed on the edge of a solidified track on the powder bed with mixed dissimilar powders having melted Cu10Sn and un-melted or partially melted In718, which results in fluctuations in the track dimensions. For unmixed dissimilar powder beds, an asymmetrical melt pool and solidified track are formed if the laser spot overlaps the interface of the dissimilar powders. The effect of hatch spacing in multiple track melting on a mixed dissimilar powder bed is also studied. It indicates that owing to the significant fluctuation in the track dimensions, the hatch spacing should be adjusted adaptively and should be less than the width of the melted zone to avoid insufficient intertrack fusion.