Organic monolayers disrupt plastic flow in metals

Sugihara, T and Udupa, A and Viswanathan, K and Davis, JM and Chandrasekar, S (2020) Organic monolayers disrupt plastic flow in metals. In: Science Advances, 6 (51).

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Abstract

Adsorbed films often influence mechanical behavior of surfaces, leading to well-known mechanochemical phenomena such as liquid metal embrittlement and environment-assisted cracking. Here, we demonstrate a mechanochemical phenomenon wherein adsorbed long-chain organic monolayers disrupt large-strain plastic deformation in metals. Using high-speed in situ imaging and post facto analysis, we show that the monolayers induce a ductile-to-brittle transition. Sinuous flow, characteristic of ductile metals, gives way to quasi-periodic fracture, typical of brittle materials, with 85 reduction in deformation forces. By independently varying surface energy and molecule chain length via molecular self-assembly, we argue that this "embrittlement"is driven by adsorbate-induced surface stress, as against surface energy reduction. Our observations, backed by modeling and molecular simulations, could provide a basis for explaining diverse mechanochemical phenomena in solids. The results also have implications for manufacturing processes such as machining and comminution, and wear. © 2020 The Authors.

Item Type:	Journal Article
Publication:	Science Advances
Publisher:	American Association for the Advancement of Science
Additional Information:	Copyright to this article belongs to American Association for the Advancement of Science
Keywords:	Embrittlement; Interfacial energy; Metals, Ductile to brittle transitions; Environment-assisted cracking; Liquid metal embrittlement; Manufacturing process; Mechanical behavior; Molecular self assembly; Molecular simulations; Molecule chain lengths, Monolayers
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	12 Feb 2021 06:03
Last Modified:	12 Feb 2021 06:03
URI:	http://eprints.iisc.ac.in/id/eprint/67521

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