Probing Laves phase formation in Ni-alloy during ultrasonic arc-welding with atomistic modelling

Ultrasonic arc-welding displays significant advantages, which are usually explained by macroscopic methods. This paper proposes a new approach to understand the mechanisms behind beneficial phenomena for nickel-based alloys. Two atomistic models were developed to depict niobium segregation and Laves phase reduction in ultrasound. It is found that an increased centrifugal force exerts on niobium atoms, and increases the equivalent force that pulls niobium atoms away from segregated region. Each niobium atom exhibits weaker ability to form Ni₂Nb in ultrasound, prohibiting niobium atoms from forming Laves phase. As validated by experimental work, Laves phase was decreased by >90vol.-%. The proposed models provide an effective tool to predict structure and property of weld metals in ultrasound at atomistic-scale.