Melting of tungsten under uniaxial and shear stresses: Molecular dynamics simulation

Understanding melting processes in refractory materials under external stresses is important and can be of particular interest in harsh environment applications ranging from aerospace to nuclear and fusion energy where these materials have to simultaneously withstand the effect of high temperatures and complex stress states in such ways, that a melting process might be initiated in extreme conditions. However, most if not all of the prior research was focused on melting phenomena in the presence of hydrostatic compression. In our work, we investigate melting phenomena in pure tungsten under uniaxial tension, uniaxial compression, hydrostatic tension, and shear stress states. We explore these relationships numerically by molecular dynamics simulations employing extended Finnis-Sinclair (EFS) potential and two-phase method and compare our results with theoretical and experimental findings reported in the literature. The melting behaviour was investigated for all the studied stress states and compared both quantitatively and qualitatively on the basis of equivalent strain, Cauchy stress tensor invariants, and maximum shear stress. For uniaxial tension, hydrostatic tension, and shear stress an abrupt decline of stress-induced melting point values was detected after certain critical stress values. New high-temperature thermo-mechanical results are correlated with intricate structural changes taking place on the atomic scale during metal-melt phase transition.