Atomistic simulations to reveal HIP-bonding mechanisms of Al6061/Al6061

A Roy and R Kalsar and M Song and VV Joshi, ACTA MATERIALIA, 281, 120402 (2024).

DOI: 10.1016/j.actamat.2024.120402

Molecular dynamics simulations were employed to understand the diffusion bonding process during hot isostatic pressing (HIP) of Al6061/Al6061 alloy. Simulations of the HIP process reveal 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 atoms occurs from the pre-existing gamma-Al2O3 to the 6061 region across the interphase interface. These oxygen atoms interact with the enriched Mg atom layer present at the existing gamma-Al2O3 and 6061 matrix to form a secondary complex Mg2Al2O5 phase. Diffusion calculations also show that transport of atoms due to the applied pressure is 4-5 orders of magnitude higher than would occur in the absence of HIP conditions. The Mg2Al2O5 phase also provides efficient pathways for the rapid transport of Mg atoms. Because of the higher diffusion coefficients observed for Mg within the phase, Mg atoms can move more swiftly compared to their diffusion within other phases such as gamma-Al2O3. This accelerated mobility facilitates the rapid movement of Mg atoms across the interface, leading to changes in the local composition and the potential growth of the Mg2Al2O5 phase.

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