Effect of Interface Reconstruction on the Mechanical Properties of Al/Al2O3 Multilayers
Abstract
The proposed research will develop atomic-scale models to firstly reproduce the morphology and mechanical properties observed in the synthetized metal/ceramic Al/Al2O3 multilayered composite, secondly based on the atomic-scale simulations, provide alternative tailoring paths to enhance desired mechanical properties. Multilayered ceramic-metal composites constituted of materials with different mechanical properties could exhibit enhancement on toughness, hardness and wear resistance as compared to individual layers. Experimental efforts to design materials with higher strength and toughness have shown that a proper combination of hard and soft multilayered composite is promising. From a theoretical perspective, Koehler proposed a model which suggests that combination of two layers with high (layer A) and low (layer B) dislocation-line energy; it should exhibit improved resistance to plastic deformation and brittle fracture compared to homogeneous A/B alloys; the key prediction suggests that significant increment on the strength of a multilayered system can be achieved by intercalating ultrathin layers (within the nanometer scale) which have large difference in the shear modulus. The motivation given by Koehler’s predictions inspired considerable studies to understanding the fundamental mechanisms that govern the mechanical properties of multilayered composites. However, a detailed understanding of the mode of strengthening of multilayered systems like Al/alumina oxide is challenging and only few studies have addressed the problem so far. State-of-the-art studies on Al/Al2O3 that combines sputtering and post annealing techniques to grow multilayered composite, which layers have a thickness of a couple of nanometers, have shown that the strength is at least one order of magnitude bigger than the predictions of the Koehler effect. To explain this enhancement, a possible mechanism of confined layer slip of single dislocation has been proposed. Experiments observed that the increase in strength is shown to be associated with the precipitation or formation of nanoclusters of Al2O3 (5 to 10 nm in diameter) within the Al matrix. The proposed study will be at ab inito level and it will start considering the ?- Al2O3 bulk structure from our previous work using density-functional theory. The knowledge on the surfaces based on this ?-Al2O3 crystal structure will be directly applied in the construction of several candidate models for Al/?-Al2O3 multilayered system. This study will consider the interface reconstruction of ultrathin multilayers of Al/?-Al2O3 interfaces which atomic structure will be resolved using simulated annealing. The main outcome of the study will be to determine the role of the reconstruction of the ?-Al2O3 in the interface on the elastic properties and the hardness. The main results might provide important clues on how to manipulate the Al/?-Al2O3 interface for tailoring desired mechanical properties.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2017
- Source ID
- N000141713063
Entities
People
- Jerzy Leszczynski
Organizations
- Jackson State University
- Office of Naval Research
- United States Navy