Simulation of the shape memory effect in a NiTi nano model system

TL;DR

This study uses molecular dynamics simulations to analyze the shape memory effect in NiTi nanoparticles, revealing how microstructure, composition, and temperature influence shape recovery without phase transition.

Contribution

It provides a detailed simulation-based analysis of shape memory behavior in NiTi nanoparticles, highlighting the effects of composition and microstructure on shape recovery.

Findings

Shape memory effect occurs via variant reorientation and twin boundary formation.

Small deviations in Ni concentration significantly affect the critical temperature for shape recovery.

Microstructure visualization supports the understanding of shape memory mechanisms.

Abstract

The shape memory behavior of a NiTi nanoparticle is analyzed by molecular dynamics simulations. After a detailed description of the equilibrium structures of the used model potential, the multi variant martensitic ground state, which depends on the geometry of the particle, is discussed. Tensile load is applied, changing the variant configuration to a single domain state with a remanent strain after unloading. Heating the particle leads to a shape memory effect without a phase transition to the austenite, but by variant reorientation and twin boundary formation at a certain temperature. These processes are described by stress-strain and strain-temperature curves, together with a visualization of the microstructure of the nanoparticle. Results are presented for five different Ni concentrations in the vicinity of 50%, showing for example, that small deviations from this ideal composition can influence the critical temperature for shape recovery significantly.