Role of twin boundary position on the yield strength of Cu nanopillars

TL;DR

This study uses atomistic simulations to demonstrate that the position of twin boundaries within Cu nanopillars significantly affects their yield strength, revealing potential for mechanical property tuning through boundary placement.

Contribution

It is the first detailed investigation showing how twin boundary position, not just spacing, influences nanopillar strength, providing new insights for material design.

Findings

Maximum strength occurs when TBs are at the center for single TB nanopillars.

Strength decreases as TBs move towards the surface in single TB structures.

Optimal TB placement at 1/4 or 1/5 of the pillar size enhances strength in double TB nanopillars.

Abstract

It is well known that the twin boundary (TB) spacing plays an important role in controlling the strength of twinned metallic nanopillars. One of the reasons attributed to this strengthening behaviour is the force exerted by the TBs on dislocations. Since the TBs exert repulsive force on dislocations and the plasticity in nanopillars is surface controlled, it is interesting to know whether the TB position from the nanowire surface has any effect on the strength of twinned nanopillars. Using atomistic simulations, here we show that the TB position significantly influences the strength of twinned nanopillars. Atomistic simulations have been performed on nanopillar containing one and two TBs and their position is varied within nanopillar from the center to the surface. The results indicate that in nanopillar containing a single TB, the strength is maximum when the TB is located at the center of the nanopillar and it decreases as the TB is shifted towards the nanopillar surface. On the other hand in nanopillar containing two TBs, the maximum strength is observed when the twin boundaries are placed at distance of one fourth or one fifth the pillar size from the surfaces and it decreases when TBs are moved on either side. The present study demonstrates that the mechanical properties of the twinned nanopillars can be controlled by carefully tailoring the position of the TBs within the nanopillars.