Dislocation breakaway from nanoparticle array linear complexions: Plasticity mechanisms and strength scaling laws

TL;DR

This study uses atomistic modeling to explore how nanoparticle array linear complexions influence dislocation behavior and strength in Ni-Al alloys, revealing a new strength scaling law distinct from classical models.

Contribution

It introduces a novel strength scaling law for dislocation breakaway from nanoparticle complexions, based on atomistic simulations and simplified models.

Findings

Dislocation breakaway involves a combined bowing and unpinning mechanism.

A new strength scaling law is proposed, differing from classical Orowan bowing.

Nanoparticle size and spacing critically affect dislocation mobility.

Abstract

Linear complexions are stable defect states, where the stress field associated with a dislocation induces a local phase transformation that remains restricted to nanoscale dimensions. As these complexions are born at the defects which control plasticity in metals, it is crucial to understand their impact on subsequent mechanical properties. In this work, atomistic modeling is used to understand how dislocation mechanics are altered by the presence of nanoparticle array linear complexions in a Ni-Al alloy. Molecular dynamics simulations are used to identify the critical shear stress needed to drive dislocation breakaway, first for nanoparticle arrays formed by Monte Carlo/molecular dynamics methods to represent realistic configurations and subsequently for simplified models that allow the effects of particle spacing and size to be varied in a controlled manner. A combined bowing and progressive unpinning mechanism is uncovered, leading to the demonstration of a new strength scaling law that differs in keys ways from classical Orowan bowing.