Atomic Origins of Friction Reduction in Metal Alloys

TL;DR

This study uses large-scale molecular dynamics simulations to uncover that pure metals exhibit high friction due to slip along crystallographic planes, while alloys reduce friction through grain boundary sliding stabilized by dissimilar atoms.

Contribution

The paper reveals the atomic-scale mechanisms behind friction differences in pure metals and alloys, highlighting the role of slip mechanisms and grain boundary stabilization.

Findings

Pure metals show high friction with slip along crystallographic planes.

Alloys exhibit reduced friction via grain boundary sliding.

Dissimilar atoms suppress grain growth, stabilizing boundaries.

Abstract

We present the results of large scale molecular dynamics simulations aimed at understanding the origins of high friction coefficients in pure metals, and their concomitant reduction in alloys and composites. We utilize a series of targeted simulations to demonstrate that different slip mechanisms are active in the two systems, leading to differing frictional behavior. Specifically, we show that in pure metals, sliding occurs along the crystallographic slip planes, whereas in alloys shear is accommodated by grain boundaries. In pure metals, there is significant grain growth induced by the applied shear stress and the slip planes are commensurate contacts with high friction. However, the presence of dissimilar atoms in alloys suppresses grain growth and stabilizes grain boundaries, leading to low friction via grain boundary sliding.