The effect of hydrogen on the evolution of intergranular cracking: a cross-scale study using first-principles and cohesive finite element methods

A combination of first-principles and cohesive finite element (CFE) cross-scale calculations is performed to examine the effect of hydrogen on the intergranular cracking of aluminum. First-principles calculations based on density functional theory are investigated to assess the adsorption and diffusion of H along the Al (111) surface and the cohesive energies of the grain boundaries (GBs) with different H concentrations. CFE calculations are used to simulate the evolution of intergranular cracking induced by hydrogen segregation in GBs. To combine first-principles calculations and CFE modelling, the GB cohesive energies are used as inputs for the fracture energies in the CFE calculations. The results show that H atoms diffuse into the interstitial sites in the bulk material and segregated to the GBs by overcoming the energy barriers. The cohesive energies of the GBs decrease linearly with increasing of H concentration. The application of these cross-scale approaches is very efficient for investigating the evolution of hydrogen induced intergranular cracking.