Mechanistic-Design of Multilayered Nanocomposites: Hierarchical Metal-MAX Materials for Tunable Strength and Toughness
Abstract
Multilayered materials have come into greater focus due to their promising mechanical, chemical and functional properties, making them practically useful in a wide range of temperatures, mechanical loadings, and environmental conditions. One primary scientific interest stems from improvements in mechanical properties such as strength, ductility, and toughness that motivates continuous research and exploration. While the vast majority of efforts primarily focus only on engineering the macroscale structure for improvement through trial-and-error, an emerging trend in the materials community lies at engineering the nanoscale mechanisms that ultimately govern the material properties. By understanding the role of the fundamental deformation or strain accommodation mechanisms, predictable alterations to the material layers are possible, which in turn can lead to physics-based tunability of the material properties. Such an approach is even more warranted, and attainable, when the layer thicknesses approach the nanoscale. The objective of the proposed research program is to leverage a fundamental understanding of the activation and confinement of deformation mechanisms directly linked to the hierarchical structure at the nanoscale in multilayered nanocomposite materials, to potentially enable tunable strength and toughness. We will accomplish this objective through an integrated computational and experimental research partnership. The proposed nanocomposite is composed of alternating metallic and MAX phase layers with a lamellar thickness reduced to the nanoscale. Unlike other multilayered systems that have been pursued in the past, the proposed metal-MAX nanocomposites detailed here are composed of a unique hierarchical laminate topology Ð as interfaces between the layers are in direct competition with the interfaces within the MAX layers for deformation. In this work we aim to leverage the recently demonstrated operative deformation mechanism within the MAX phase layersÐ termed ripplocation Ð which is noted to govern the unprecedented strain reversibility and strain energy accommodation potential in layered solids. Currently, there is no literature on the tunability of MAX phases by controlling the activation barrier of ripplocation nucleation. We propose to tune the strength and ductility of the metal-MAX multilayer by confining the MAX phase to suppress its propensity for ripplocation nucleation, thus enabling cooperation/competition of both dislocations and ripplocations during deformation. The objectives of this combined modeling and experimental research are to: a) synthesize and model multi-layered nanocomposites composed of alternating metallic and MAX phase layers with a lamellar thickness reduced to the nanoscale, b) establish a fundamental understanding of the nanoscale deformation mechanisms and microstructure-property relationships, and c) formulate and validate atomistic models that outline the premise for controlling the activation of specific deformation mode(s) through the hierarchical structure of metal-MAX nanolaminates, thus tuning their mechanical properties to achieve improved strength and toughness.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 04, 2019
- Source ID
- W911NF1910389
Entities
People
- Garritt J Tucker
Organizations
- Army Contracting Command
- Colorado School of Mines
- United States Army