Critical Analysis of an FeP Empirical Potential Employed to Study Fracture of Metallic Glasses

TL;DR

This paper critically examines an empirical FeP potential used in molecular dynamics to study metallic glass fracture, revealing spinodal decomposition and embrittlement effects that may not reflect real alloy behavior.

Contribution

It identifies limitations of the empirical potential, showing it induces microstructural artifacts like segregation and brittle fracture pathways not present in actual alloys.

Findings

Spinodal decomposition occurs in the studied composition range.

Phosphorous segregation causes a transition from ductility to brittleness.

Toughness decreases linearly with compositional segregation.

Abstract

An empirical potential that has been widely used to perform molecular dynamics studies on the fracture behavior of FeP metallic glasses is shown to exhibit spinodal decomposition in the composition range commonly studied. The phosphorous segregation induces a transition from ductility to brittleness. During brittle fracture the atomically sharp crack tip propagates along a percolating path with higher P concentration. This embrittlement is observed to occur over a wide range of chemical compositions, and toughness decreases linearly with the degree of compositional segregation over the entire the regime studied. Stable glass forming alloys that can be quenched at low quench rates do not, as a rule, exhibit such thermodynamically unstable behavior near to or above their glass transition temperatures. Hence, the microstructures exhibited in these simulations are unlikely to reflect the actual microstructures or fracture behaviors of the glassy alloys they seek to elucidate.