Local strain release due to microcracking in laser melted tungsten

Residual stresses in laser powder bed fusion typically reach the yield stress of the material, leading to part deformations or even cracking. Previous work showed that there were no measureable residual stresses present in tungsten parts, but also that these parts were riddled with a microcrack network. In this work, the strain relaxation due to microcracking is directly measured by applying one-dimensional DIC-like techniques to high speed videos obtained of laser melting of tungsten single tracks. Coupled thermomechanical models match the measured strain release and confirm that the release is asymmetrical, with lower strains released on the side of the crack facing the melt pool. Finally, the distance between cracks correlates with the distance over which strains are released by the cracking event, showing that microcracks relax all residual stresses during laser powder bed fusion of tungsten.