Multiphase-field modelling of hydrogen pore evolution during alloy solidification

Abstract

Gas porosity is recognized as one of the most common defects that can severely deteriorate the mechanical properties of solidified materials. Simulating the gas porosity in castings is challenging due to intricate multiphase interaction. In this work, a multiphase-field model is developed to simulate the evolution of both solid phase and hydrogen pore during solidification in the Al-Cu alloy. The driving forces for the solid-liquid and liquid-gas transitions are the undercooling and pressure difference respectively. Results show that the presence of hydrogen pore substantially changes the dendrite network. The Cu element accumulates near the solid-liquid interface due to solute partition. The pore causes a local hydrogen reservoir and Cu vacuum region, which elevates the average hydrogen content and retards the dendrite growth by blocking Cu diffusion.