Local Mechanical Stability of the Aluminum / Carbon (Amorphous) and Aluminum / SiO 2 (Amorphous) Interface at Extrinsic
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LOCAL MECHANICAL STABILITY OF THE ALUMINUM / CARBON (AMORPHOUS) AND ALUMINUM / SiO2 (AMORPHOUS) INTERFACE AT EXTRINSIC DISLOCATIONS E.D. McCarty and S.A. Hackney DepL of Metallurgical Engineering, Michigan Technological University, Houghton, MI 49931 ABSTRACT
Interfaces between Al and amorphous C or amorphous Sic2 were prepared by sputter deposition of the ceramic phases onto the sputter cleaned surfaces of large grain Al. In situ TEM was used to study the behavior of the extrinsic dislocations (slip traces) at the metal/ceramic interface formed by the motion of Al lattice dislocations which intersect the interphase boundary plane. The proximity of the extrinsic lattice dislocation to the metal/ceramic interface places this interphase boundary under a highly localized stress. Relaxation behavior of extrinsic defects at the interface region is a function of the defect standoff distance from the interface, image stress and the applied stress. An experimental technique is proposed to estimate the minimum shear stress the various interfacial regions are able to withstand. Research supported by the Department of Energy. INTRODUCTION
The local response of bimaterial interfaces to applied loads is thought to be of great relevance to a variety of technologically important processes. The behavior of thin film epitaxial interfaces at the point of coherency breaking [1] and bimaterial interfacial fracture [2] are two cases where atomic level interfacial bonding under stress has been considered in detail from a theoretical point of view. The questions which arise about the local behavior of the interface appear to be associated with what assumptions are realistic concerning continuity of stress and displacements at the boundary between two different materials. The concepts of interface sliding, interface fracture, and interface modulus have been introduced into the literature in an attempt to treat the manner in which the local interface response will contribute to macroscopic behavior. These processes and properties are considered to be localized to the interface or the interfacial region and the introduction of such ideas suggests a conviction that the interfacial region will behave in a substantially different manner than the bulk. Experimental studies of interfacial properties must therefore be designed to extract information about the very small volume of material which constitutes the interfacial region. Macroscopic experimental measurements can be made on the work required to cause the decohesion of bimaterial interfaces under tension or shear, for example, and it may be possible to extract from these results the atomic scale interface response if the work related to the deformation of the bulk materials can be separated from the response of the interfacial region. However, it may be of interest to attempt studies which directly examine the local response of the interfacial region to applied stress. This work presents a type of dynamic transmission electron microscopy study of the local bimaterial interface response t
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