Effects of quenching rate on crack propagation in NiAl alloy using molecular dynamics

• The crack growth of pre-cracked NiAl alloy is investigated by MD.
• The effects of quenching rate on crack deformation are evaluated.
• The amorphous and crystalline structures exhibit distinct fracture behaviors.
• Ductile failure occurs on the shear band for faster quenching rate.

The crack growth and propagation of pre-cracked NiAl alloy prepared at different quenching rates under mode I loading conditions were investigated using molecular dynamics (MD) simulation based on the many-body embedded atom method (EAM) potential. The quench rate effects were evaluated in terms of atomic trajectories, common neighbor analysis (CNA), radical distribution function (RDF) and glass transition. The simulation results clearly show that as the quenching rate increases ten times from 0.5 K/ps to 50 K/ps, the volume after quenching will increase by approximately 1%. The amorphous structure and crystalline structure exhibit two distinct types of fracture behavior between quenching rates of 0.25–50 K/ps. In the amorphous state, the critical stress increases with decreasing quenching rate. Moreover, two shear bands and the shear transformation zones (STZ) extend along a direction of about 45° with respect to the horizontal direction away from the crack tip.

Atomic displacement vectors and local shear strain with quenching rates of (a) 50 K/ps and (b) 0.25 K/ps. The arrow denotes the atomic displacement vector, and atoms are colored according to their local shear strains.Figure optionsDownload as PowerPoint slide