Atomistic Simulation of Phase Transformation and Fracture in Ordered Intermetallics

A review of computer simulations carried out at our Center for Materials Simulation applied to stud-ying the different atomistic processes of fracture and displacive (martensitic) transformations is pres-ented.Since these processes can happen extremely rapidly and involve only a small number of atomsinitially,they are ideally suited for molecular dynamics type simulations which can currently onlyspan times of the order of one nanosecond and involve at most a million atoms.A method is alsopresented for simulating much larger samples for much longer times through the use of theMonte-Carlo technique combined with a Ginzburg-Landau free energy functional,where the rele-vant material parameters are determined from molecular dynamics runs on the same alloy system.Asummary of studies on fracture simulations in the ordered intermetallics NiAI and RuAl is given,aswell as a discussion of the observation and analysis of the heterogeneous nucleation of themartensitic transformation in NiAI which shows localized soft mode phenomena.It is concluded thatcomputer simulations,whether of the atomistic molecular dynamics type or of the larger scaleMonte-Carlo variety,are rapidly becoming of greater and greater use in understanding the propertiesof solids under a wide rancle of temperature and stress conditions.

Atomistic Simulation of Phase Transformation and Fracture in Ordered Intermetallics

A review of computer simulations carried out at our Center for Materials Simulation applied to stud- ying the different atomistic processes of fracture and displacive (martensitic) transformations is pres- ented.Since these processes can happen extremely rapidly and involve only a small number of atoms initially,they are ideally suited for molecular dynamics type simulations which can currently only span times of the order of one nanosecond and involve at most a million atoms.A method is also presented for simulating much larger samples for much longer times through the use of the Monte-Carlo technique combined with a Ginzburg-Landau free energy functional,where the rele- vant material parameters are determined from molecular dynamics runs on the same alloy system.A summary of studies on fracture simulations in the ordered intermetallics NiAI and RuAl is given,as well as a discussion of the observation and analysis of the heterogeneous nucleation of the martensitic transformation in NiAI which shows localized soft mode phenomena.It is concluded that computer simulations,whether of the atomistic molecular dynamics type or of the larger scale Monte-Carlo variety,are rapidly becoming of greater and greater use in understanding the properties of solids under a wide rancle of temperature and stress conditions.