PNNL

Abstract

Molecular dynamics simulations were employed to understand the diffusion bonding process during hot isostatic pressing (HIP) of Al6061/Al6061. Dynamics of the process reveal the interesting atomistic phenomena that are difficult or unlikely to be observed experimentally and provide useful insights into the mechanism of diffusion and bonding. The results reveal that at the start of the HIP process a massive incursion of oxygen occurs from the pre-existing ?-Al2O3 to 6061 region across the interphase interface. These oxygen atoms interact with the enriched Mg atom layer present at the existing ?-Al2O3 and 6061 matrix to form a secondary complex phase Mg2Al2O5. Diffusion calculations also show that the transportation of atoms due to the applied pressure is 4-5 orders of magnitude higher than that in the absence of HIP conditions. The formation of this phase also provides efficient pathways for the rapid transport of Mg atoms. Due to the higher diffusion coefficients observed for Mg within the phase, Mg atoms can move more swiftly compared to their diffusion within other phases like ?-Al2O3. This accelerated mobility facilitates the quick movement of Mg atoms across the interface thus promoting improved adhesion between neighboring plates and a robust bonding interface.