Enhanced strength and fracture characteristics of the TiAl/Ti2AlNb laminated composite

As part of a broad program on composite materials, the role of the interface on the micromechanics of deformation of metal-matrix composites is being studied. The approach is to correlate elastic behavior, micro and macroyielding, flow, and fracture behavior with associated structural detail (dislocation substructure, fracture characteristics) and stress-state. This provides an understanding of the mode of deformation from an atomistic viewpoint; a critical evaluation can then be made of existing models of composite behavior based on continuum mechanics. This paper covers the electron microscopy (transmission, fractography, scanning microscopy) of two distinct forms of composite material: conventional fiber-reinforced (aluminum-stainless steel) and directionally solidified eutectic alloys (aluminum-copper). In the former, the interface is in the form of a compound and/or solid solution whereas in directionally solidified alloys, the interface consists of a precise crystallographic boundary between the two constituents of the eutectic.

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A TEM study of the interface between organic matrix and aragonite in a biological hard tissue, nacre

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100129759 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1024-1025

Author(s):

Jun Liu ◽

Katie E. Gunnison ◽

Mehmet Sarikaya ◽

Ilhan A. Aksay

Keyword(s):

Mechanical Properties ◽

Ion Beam ◽

Laminated Composite ◽

Organic Matrix ◽

Pearl Oyster ◽

Interfacial Structure ◽

Interfacial Region ◽

Thin Sections ◽

Organic Layers ◽

Transmission Electron

The interfacial structure between the organic and inorganic phases in biological hard tissues plays an important role in controlling the growth and the mechanical properties of these materials. The objective of this work was to investigate these interfaces in nacre by transmission electron microscopy. The nacreous section of several different seashells -- abalone, pearl oyster, and nautilus -- were studied. Nacre is a laminated composite material consisting of CaCO3 platelets (constituting > 90 vol.% of the overall composite) separated by a thin organic matrix. Nacre is of interest to biomimetics because of its highly ordered structure and a good combination of mechanical properties. In this study, electron transparent thin sections were prepared by a low-temperature ion-beam milling procedure and by ultramicrotomy. To reveal structures in the organic layers as well as in the interfacial region, samples were further subjected to chemical fixation and labeling, or chemical etching. All experiments were performed with a Philips 430T TEM/STEM at 300 keV with a liquid Nitrogen sample holder.

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