Analysis of laser-induced microcracking in tungsten under additive manufacturing conditions: Experiment and simulation

Tungsten is receiving increasing interest as a plasma facing material in the ITER fusion reactor, collimators, and other structural, high temperature applications. Concurrently, there is a demand for manufacturing techniques capable of processing tungsten into the desired geometries. Additive manufacturing is a promising technique able to produce complex parts, but the structural integrity is compromised by microcracking. This work combines thermomechanical simulations with in situ high-speed video of microcracking in single laser-melted tracks, visualizing the ductile-to-brittle transition. Microcracking is shown to occur in a narrow temperature interval between 450 K-650 K, and to be strain rate dependent. The size of the crack-affected area around the scan track is determined by the maximum Von Mises residual stress, whereas crack network morphology depends on the local orientation of the principal stress. The fundamental understanding provided by this work contributes to future efforts in crack free, additively manufactured tungsten. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.