Molecular dynamics studies on formation of stacking fault tetrahedra in FCC metals

Abstract

The formation of stacking fault tetrahedra (SFT) based on the vacancy clustering mechanism and Frank loop in case of face centered cubic (FCC) metals and alloys is widely accepted, but the corresponding research for SFT formation without the involvement of Frank loop and interaction of dislocations is not well understood. In this article, we attempt to explain the formation of SFT from vacancies, voids and nanoindentation process in case of low stacking fault energy (Ag) and high stacking fault energy (Ni) FCC metals. The atomic scale processes are simulated and step wise evolution of vacancy cluster and dislocation loops to SFT are provided by molecular dynamics method. We describe in this atomistic simulation that the voids containing 13 and 43 vacancy atoms can rearrange themselves to transform to SFT without going through the Frank loop. The present work has also demonstrated the formation of SFT during nano indentation of (111) surface of Ag and Ni through interactions of Shockley partials without the involvement of vacancies or Frank loop.