Crystal plasticity analysis of the evolutions of temperature, stress and dislocation in additively manufactured tungsten

Additive manufacturing (AM) has brought new opportunities for the fabrication of refractory metal tungsten (W). However, the cracking issue in additive manufactured pure W has not been solved, restricting its application. The cracking behavior is associated with the high residual stress, which is caused by the high temperature gradient and cooling rate during AM, as well as the internal brittleness of W. In order to solve this problem, the evolution of the internal microstructure and the corresponding thermal and loading conditions during AM has to be systematically investigated, but the related work is very rare. In the current work, a thermal-mechanical coupled dislocation-based crystal plasticity model is developed, which considers the temperature dependent plasticity induced by the thermal-activated kink-pair mechanism of screw dislocation. This model is applied to investigate the evolution of temperature, stress, and dislocation behaviors in single crystal and polycrystalline W during AM. The influences of crystal orientation and adding alloying element Ta are also discussed from the microscopic and macroscopic perspectives.